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GENERATOR PROTECTION IN BPCL-KOCHI
REFINERY USING NUMERICAL RELAY
INTRODUCTION
The aim of this project was to analyze and upgrade the existing generator protection system in BPCL-Kochi Refinery, Kochi. Power generation occupies the prime place in power system. Industrial and commercial power system may include generator as a local source of energy. These generators supply all or part of the total energy required or they provide emergency power in the event of a failure of the normal source of energy.
Generator protection requires the consideration of many abnormal conditions that are not present with other system elements. Where the system is unaltered, it should be provided with automatic protection against all harmful conditions.
We analyzed and studied the existing generator protection relays used in BPCL-KR. There different types of protection employ different types of relays.
With the technological advances being made in generation protection section, the generator protection using new methods have gathered momentum. From our analysis on various relays in generator protection in BPCL-KR, we suggest using one numerical relay instead of all existing electromechanical relays.
PROJECT REPORT
Submitted by
AJU.M.PAULOSE BUOY THOMAS HAPPY VARGHESE RONY ITTAN SUJITH.S
BPCL-KOCHI REFINERY - PROFILE
M/S Kochi Refineries Ltd, its story starts on April 27, 1963. That was when the Govt, of India, Philips Petroleum Company of USA and Duncan Brothers of Calcutta signed an agreement for the construction of a petroleum refinery of south India.
M/S Kochi Refineries Ltd formally known as M/S Cochin Refineries Ltd was formally registered on 6th September 1963 at Ernakulum. Philips International Corporation was the primary contractors for the construction of the refinery. The work was started on March 1964 and the first unit came in stream just after 29 months in September 1966. Former Indian Prime minister Mrs. Indira Gandhi dedicated Kochi Refineries Ltd to the nation on 23rd September 1966.
The refinery then has a design capacity of 2.5 million metric tones per annum which was increased to 3.3 million metric tones per annum in 1973. Production of liquefied petroleum gas (LPG) and aviation turbine fuel (ATF) after this expansion. Refinery capacity was further enhanced to 45 million metric tones per annum in November 1984 when fluidized catalytic cracking unit (FCCU) was added. In December 1994, refinery capacity was increased to 7.5 million metric tones per annum. A fuel gas desulphurization unit was installed as a part of this project to minimize the emission of S02. Kochi Refineries Ltd entered the petrochemical sector in 1989 when the aromatic production facilitates with a design capacity of 87200 tones per annum of benzene and 12000 tones per annum of toluene was commissioned.
REFINERY PRODUCTS
OIL PRODUCTS PRODUCED IN BHARAT PETROltUM AND THEIR USES
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Polypropylene Feedstock Liquefied Petroleum Gas Automotive LPG Food Grade Hexane SBP 55/115 Benzene Toluene Naphtha -RIL Naphtha - RPL Naphtha - NTPC Naphtha - TANNIRBAVI Naphtha -N (coastal/normal) Naphtha for PPN High Aromatics Naphtha (export) Low Aromatics Naphtha (normal) Low Aromatics Naphtha (export) Motor Gasoline II Mineral Turpentine Aviation Turbine Fuel (atl) Aviation Turbine Fuel 1 Superior Kerosene High Speed Diesel Oil High Speed Diesel Oil II High Speed Diesel Oil II High Speed Diesel (LSHF) Light Diesel Oil Fuel Oil DG Grade Bitumen Sulphur
CAPTIVE POWER PLANT (CPP)
A captive power plant of 22 MW was commissioned in 1991. An additional captive power plant of 17.8 MW was commissioned in 1998. '
Captive Power Plant (CPP) is the heart of KRL. It has a gas turbine generator (GTG) and a steam turbine generator (STG) which caters the electrical load of refinery. BPCL-KR also, has 66Kv feeders from KSEB, Kalamassery Substation with a contract maximum demand of 20MVA. The 66KV feeder's line 1 and line 2 are tapped from (Kalamassery-Vyttila) No.l feeder and (Kalamassery-Vyttila) No.2 feeder respectively. The total running load of BPCL-KR comes to around 36MW out of which 5MW is being continuously drawn from KSEB and remaining 31MW will be shared by GTG, STG and TG.KSEB power being unstable used for feeding non-critical loads and captive generation is used for feeding critical loads. The BPCL-KR consumes about 7.5 lakhs units of electrical energy on an average per day. The generated/imported from KSEB at captive power plant is distributed to different plants using XLPE cables at 11KV level through two substations namely CPP substation and New MRS substation, process substation, FCCU, Revamp substation, ACTP substation, CPP offsite substation, unit station transformers receives power from CPP substation 11KV switch gear and CDU-2 substation, ARU substation, Naphtha Revamp substation, PIB substation and colony sector-1 substation receives power from New MRS substation. BPCL-KR electrical system also consists of around 2500 motors, 80 transformers, 40 substations/ MCC rooms.
TECHNICAL PARTICULARS OF GAS TURBINE GENERATOR
General Turbo generator
Type TARI 700-28P
Apparent power 27.5MVA
Active power 22.0MW
Current 1443Amps
Voltage 11KV _10%
Speed 3000RPM
Frequency 50HZ
Power factor 0.8 Lag
Interconnection of Stator winding - Star
Unbalance loading 10%
Field current for rated output Approx. 581 Amps
Cooling water inlet temperature 33 C
Cooling water outlet temperature 34 C
TECHNICAL PARTICULARS OF STEAM TURBINE GENERATOR
of generator
Voltage
Armature current Revolutions Frequency Number of phases . Number of poles Power factor Insulation class
Rating
Type of outer housing (With air cooler) Ventilation type Field type
. Bearing oil feed system Guaranteed over speed Applicable standard Excitation method
GGAK517A-B01A-F01
22.25MVA
17.8MW
11KV
1168 Amps
1500RPM
50HZ
3
4
. 0.8 Lag Stator-F Rotor-F Continuous
Totally enclosed, internal Cooling type
Self ventilation
Rotating field type
Automatic centre
Aligning type cylindrical
Bearing
Forced oil feed
1800RPM for 2 minute
JEC 114(1979)
Separate excitation (Stator Side)
NEED FOR PROTECTION
Protection is installed to detect faults occurrences and isolate the faulty equipments so that the damage to the faulty equipment is limited and disruption of supplies to the adjacent unaffected equipment is minimized.
In a power system consisting of generators, motors, transformers etc, it is inevitable that sooner or later some fault may occur somewhere. When a fault occurs it is must be quickly detected the faulty equipment must be disconnected from the system. If fault are not detected quickly it cause unnecessary interruption of service to the customers and damage to other connected equipments.
I Generally fuse performs the function of detection and interruption but it is limited only to low voltage circuits. For high voltage circuits, relays and circuit breakers are used.
So protection must detect faults and abnormal working conditions and isolate the faulty working conditions and isolate the faulty equipment so as to limit damage caused by fault energy and to limit effect on rest of the system
We usually think of an electric power system in terms of its more impressive parts-the
big
Generating stations, transformers, high-voltage lines, etc. While these are some of the basic Elements, there are many other necessary and fascinating components. Protective relaying is one of these. The role of protective relaying in electric-power-system design and operation is explained by a brief examination of the over-all background. There are three aspects of a power system that will serve the purposes of this examination. These aspects are as follows: . 1. Normal operation
2. Prevention of electrical failure.
3. Mitigation of the effects of electrical failure.
The term normal operation assumes no failures of equipment, no mistakes of ' personnel, no acts of God. It involves the minimum requirements for supplying the existing load and a certain amount of anticipated future load. Some of the considerations are:
A. Choice between hydro, steam, or other sources of power.
B. Location of generating stations.
C. Transmission of power to the load.
D. Study of the load characteristics and planning for its future growth.
E. Metering
F. Voltage and frequency regulation.
G. System operation.
H. E. Normal maintenance.
I The provisions for normal operation involve the major expense for equipment and . Operation, but a system designed according to this aspect alone could not possibly meet Present-day requirements. Electrical equipment failures would cause intolerable outages. There must be additional provisions to minimize damage to equipment and interruptions To the service when failures occur.
Two recourses are open: (1) to incorporate features of design aimed at preventing failures and (2) to include provisions for mitigating the effects of failure when it occurs. Modern power-system design employs varying degrees of both recourses, as dictated by the economics of any particular situation. Notable advances continue to be made toward greater reliability. But also, increasingly greater reliance is being placed on electric power. Consequently, even though the probability of failure is decreased, the tolerance of the . possible harm to the service is also decreased. But it is futile-or at least not economically justifiable-to try to prevent failures completely. Sooner or later the law of diminishing returns makes itself felt. Where this occurs will vary between systems and between parts of a system, but, when this point is reached, further expenditure for failure prevention is discouraged. It is much more profitable, then, to let some failures occur and to provide for mitigating their effects. The type of electrical failure that causes greatest concern is the short circuit, or fault as it is usually called, but there are other abnormal operating conditions peculiar to certain elements of the system that also require attention.
Some of the features of design and operation aimed at preventing electrical failure are:
A. Provision of adequate insulation.
B. Coordination of insulation strength with the capabilities of lightning arresters.
C. Use of overhead ground wires and low tower-footing resistance.
D. Design for mechanical strength to reduce exposure, and to minimize the likelihood of
failure causable by animals, birds, insects, dirt, sleet, etc.
E. Proper operation and maintenance practices.
Some of the features of design and operation for mitigating the effects of failure are:
A. Features that mitigate the immediate effects of an electrical failure.
1. Design to limit the magnitude of short-circuit current. 1
a. By avoiding too large concentrations of generating capacity.
b. By using current-limiting impedance.
2. Design to withstand mechanical stresses and heating owing to short-circuit currents.
3. Time-delay under voltage devices on circuit breakers to prevent dropping loads during momentary voltage dips.
4. Ground-fault neutralizers (Petersen coils).
B. Features for promptly disconnecting the faulty element.
1. Protective relaying.
2. Circuit breakers with sufficient interrupting capacity.
3. Fuses.
C. Features that mitigate the loss of the faulty element.
1. Alternate circuits.
2. Reserve generator and transformer capacity.
3. Automatic reclosing.
D. Features that operate throughout the period from the inception of the
Fault until after its removal, to maintain voltage and stability.
1. Automatic voltage regulation. ' 2. Stability characteristics of generators.
E. Means for observing the electiveness of the foregoing features.
1. Automatic oscillographs.
2. Efficient human observation and record keeping.
F. Frequent surveys as system changes or additions are made, to be sure that the
foregoing features are still adequate.
Thus, protective relaying is one of several features of system design concerned with minimizing damage to equipment and interruptions to service when electrical failures ' occur. When we say that relays protect, we mean that, together with other equipment, the relays help to minimize damage and improve service. It will be evident that all the mitigation features are dependent on one another for successfully minimizing the effects of failure. Therefore, the capabilities and the application requirements of protective-relaying equipments should be considered concurrently with the other features. This statement is emphasized because there is sometimes a tendency to think of the protective-relaying equipment after all other design considerations are irrevocably settled. Within economic limits, an electric power system should be designed so that it can be adequately protected.
FAULT RISKS
Severe damage to the faulted equipment
Excessive current may flow
Causes burning of conductors or equipment winding
Arcing-energy dissipation
Risk of explosion for oil filled switch area or when in hazardous environments Damage to adjacent plants
Damage to staff or personnel
Risk of shock from direct contact with the faulted equipment
Danger of potential rises in exposed metal work accessible to touch
Fumes released by burning insulation
Burns etc
Disruption to adjacent plants
Prolonged voltage dips cause other equipment to stall
Loss of synchronism for synchronous generators/motors
PROTECTION RELAYS
Protection relays can be classified in various ways depending on their construction, functions and are discussed below.
CLASSIFICAION OF PROTECTIVE RELAYS BASED ON TECHNOLOGY
Protective relays can be broadly classified into the following categories depending on the technology used for their construction and operation.
1. Electromagnetic relays j 2. Static relays 3. Microprocessor-based relays
Electromagnetic relays:-
It includes attracted armature, moving coil and induction disc and : Type relays. Electromagnetic relays contain an electromagnet (or permanent magnet) and a moving part. When the actuating quantity exceeds a certain predetermined value, an operating torque is developed which is applied on the moving part. This causes the moving part to travel and to finally close a contact to energize the trip coil of the breaker.
Static relays:-
t
Static relays contains electronic circuits which may contain transistors, ICs, diodes and other electronic components. There is a comparator circuit in the relay, which compares two or more voltages and gives an output, which is applied to either a slave ready or a thyristor circuit. The slave ready is an electromagnetic relay which finally closes the contact. A static relay containing a slave ready is semi-static relay. A relay using thyristor circuit is a wholly static relay. Static relay possess the advantage of having low burden on CT and PT, fast operation, absence of mechanical inertia and contact trouble, long life and less maintenance
Static relays have proved to be superior to electromagnetic relays and they are being used for the protection of important lines, power stations and substations. Yet they have not completely replaced electromagnetic relays. Static relays are treated as an addition to family of relays. Electromagnetic relays continue to be in use because of their simplicity and low cost. Their maintenance can be done by less qualified personal, where as the maintenance and repair of static relays requires personnel's trained in solid-state device.
Microprocessor-based protective relays;-
Microprocessor-based protective relays are the latest development in this area. With the development in VLSI Technology, Sophisticated and fast microprocessor are coming up. Their applications to the problems of protective relaying schemes are of current interests to power engineers. The inherit advantages of microprocessor-based relays over static relays with or a very limited range of applications, are attractive, flexibility due to their programmable approach. Microprocessor-based protective relays can provide protection at low cost and compete with conventional relays. The present downward trend in the cost of large-scale integrated circuit will encourage wide applications of microprocessor-based applications of microprocessor-based relays for the protection modern complex power network.
FUNCTION OF PROTECTIVE RELAYING
The function of protective relaying is to cause the prompt removal from service of any element of a power system when it suffers a short circuit, or when it starts to operate in any abnormal manner that might cause damage or otherwise interfere with the effective operation of the rest of the system. The relaying equipment is aided in this task by circuit breakers that are capable of disconnecting the faulty element when they are called upon to do so by the relaying equipment.
Circuit breakers are generally located so that each generator, transformer, bus, transmission line, etc., can be completely disconnected from the rest of the system. These circuit breakers must have sufficient capacity so that they can carry momentarily the maximum short-circuit current that can flow through them, and then interrupt this current; they must also withstand closing in on such a short circuit and then interrupting it according to certain prescribed standards.
Fusing is employed where protective relays and circuit breakers are not economically justifiable.
Although the principal function of protective relaying is to mitigate the effects of short-circuits, other abnormal operating conditions arise that also require the services of protective relaying. This is particularly true of generators and motors.
A secondary function of protective relaying is to provide indication of the location and type of failure. Such data not only assist in expediting repair but also, by comparison with human observation and automatic oscillograph records, they provide means for analyzing the effectiveness of the fault-prevention and mitigation features including the protective relaying itself.
HOW DO PROTECTIVE RELAYS OPERATE
All relays used for short-circuit protection, and many other types also, operate by virtue of the current and/or voltage supplied to them by current and voltage transformers connected in various combinations to the system element that is to be protected. Through individual or relative changes in these two quantities, failures signal their presence, type, And location to the protective relays. For every type and location of failure, there is some distinctive difference in these quantities, and there are various types of protective-relaying equipments available, each of which is designed to recognize a particular difference and to .operate in response to it.6
More possible differences exist in these quantities than one might suspect. Differences in each quantity are possible in one or more of the following:
A. Magnitude.
B. Frequency.
C. Phase angle.
D. Duration.
E. Rate of change.
F. Direction or order of change.
G. Harmonics or wave shape.
Then, when both voltage and current are considered in combination, or relative to similar quantities at different locations, one can begin to realize the resources available for discriminatory purposes. It is a fortunate circumstance that, although Nature in her contrary way has imposed the burden of electric-power-system failure, she has at the same time provided us with a means for combat.
ASPECTS OF PROTECTION SYSTEM
Dependability/Reliability { Protection must operate when required
Failure to operate can be extremely damaging and disruptive
Faults are rare: Protection must operate even after years of inactivity
Improved by use of back up protection and duplicate protection
Security/Stability
Protection must not operate when not required to e.g., due to
Load Switching
Faults on other parts of the system .
Recoverable process swings m Speed
Fast operation;
Minimizes damage and danger
Minimizes system instability
Discrimination and security can be costly to achieve as it generally involves additional signaling/communication equipment
Cost
The cost of protection is equivalent to an insurance policy against damage to plant, And loss of supply and customer goodwill
Acceptable cost is based on a balance of economics and technical factors. Cost of protection should be balanced against cost of potential hazards
There is an economic limit on what we can spent
TECHNOLOGY COMPARISON FOR PROTECTIVE RELAYS
SI. No SUBJECT ELECTRO-MECHANICAL STATIC/ ELECTRONIC NUMERICAL
1 Measuring elements/ Hardware Induction disc, Electromagnets, Induction cup, Balance Beam Discrete R, L, C Transistors, Analogue ICs comparators Microprocessors, Digital ICs, Digital signal processors
2 Measuring method Electrical quantities converted into mechanical force, torque Level detectors, comparison with reference value in analogue comparator A/D conversion,
Numerical algorithm techniques evaluate trip criteria
3 Timing function Mechanical clock works, dashpot Static timers Counters
4 Sequence of events Not possible Not possible Provided
5 Visual indication Flags, targets LEDs LEDs, LCD Display
Trip Additional trip duty relay required Additional trip duty Trip duty contact
0 command
relay required inbuilt
7 Self monitoring No Yes Yes
8 Construction size Bulky Modular, compact Most compact
9 Temp. Stability Yes No Yes
10 Contacts Assignments Fixed Fixed Freely Marshable
11 Parameter Setting Plug setting, Dial setting Thumb Wheel, Potentiometers, Dual in line switches Keypad for Numeric values
12 Binary inputs for adaptive relaying Not Available Not Available Freely Marshable from 24v to 250v
13 CT loading/ Burden 8- 10 VA 1 VA <0.5 VA
14 CT offset adjustment No No Yes
15 Vibration proof No Yes Yes
16 Harmonic Immunity No Possible through Analog filtering Yes, digital filtering incorporated
17 Calibration Frequently required as settings drift due to ageing Required as settings drift due to ageing Not required as settings are stored in memory in digital format
18 Auxiliary supply Required Required Required
19 Electromagnetic/ Electrostatic/ high freq. disturbance Immune Susceptible Immune
20 Multiple characteristics Not possible Not possible Possible
21 Integrated protection functions Not possible Not possible Possible
22 Range of settings Limited Wide Wide
23 Operational value indication Not possible Possible Possible
24 Fault disturbance recording Not possible Not possible Possible
25 Digital communication port Not possible Not possible Available
26 Commissioning support from relay No No Yes
GENERATOR PROTECTION
Short circuit protection of stator winding Turn to turn faults in stator winding Stator ground fault protection Protection against stator open circuit Stator overheating protection Over voltage and under voltage protection Loss of synchronism protection Field ground fault protection
Protection against rotor overheating protection because of unbalanced three phase currents Loss of excitation protection
Protection against rotor overheating because of over excitation
Protection against motoring
Over speed protection
Pole slipping protection
Protection against Reverse power
External fault back up protection
EXISTING PROTECTION SYSTEM IN BPCL-KR Instantaneous voltage relay
Instantaneous over voltage protection of generators, capacitors etc. definite time protection under voltage protection of ac motors, Automatic voltage change over schemes and other instantaneous and definite time under voltage and over voltage applications requiring adjustable settings.
Instantaneous protection against abnormal voltage conditions such as over voltages, under voltage or non voltage in ac and dc circuits and for definite time operation when used in used in conjunction with a timer.
A standard attracted armature type relay with seven equal settings adjustable on a plug board .A DC coil is used with an internally mounted bridge rectifier to obtain a drop off/pick up ratio of the order of 90%. A resistance connected in series with the coil is tapped suitably and the taps are connected to the plug board to obtain seven equal setting. A capacitor is used to serve as a filter unit for the bridge rectifier and it also acts as a surge suppressor for protecting the diodes of the bridge rectifier against high voltage terminals. The DC coil is filtered with a normally open light duty contact which is arranged to energize an auxiliary unit which provides the necessary output contacts. Type VAGM22 is a single pole relay with its auxiliary unit.
Sensitive Earth fault relay
The relay type CTU15 provides protection against very low current earth faults and has setting down to 1% of current transformer rating. An adjustable time delay ensures stability during switching or transient conditions and allows adequate grading with other protection at high resetting ratio almost 99% of pickup current ensure that the relay will reset at a current only marginally below the pick up level. This permits a relay setting level just above the maximum residual current from the CT under quiescent condition.
An extremely low voltage burden allows the relays to share current transformer with existing protection even when the CT are of comparatively low output. The CTU15 relays can be used with economically designed core balance CT s also.
Trip circuit supervision relay
After closing or continuous supervision of the trip CBs. Type VAX relays are basically standard attracted armature unit of simple and robust construction. They are arranged to initiate an audible alarm and visual indication if the mechanism does not operate. Two versions of relay monitors the trip circuit only when the circuit breakers is closed (after closing supervision only) while type vax31 relay monitors the trip circuit continuously (both pre-closing and after closing supervision). Both detect the following conditions
1. Failure of trip supply
2. Open circuit of trip coil or trip circuit wiring Failure of mechanism to complete the tripping operation
High speed tripping relays
High speed tripping duties, where a number of simultaneous switching operations are required. A fast operating multi contact attracted armature relay with a high degree of mechanical stability. Type VAJH 13 relays has hand reset contacts and is available in two versions high burden and low burden. Type VAJS 13 has self reset contact and is a low burden relay with hand reset contacts is recommended where supervision of trip relay coil is decided. The operating current for all versions is in excess of 0.025 amps. And the relays are suitable for operation on DC supplies fitted with a negative potential biasing device. Voltage band for satisfactory operation 50 to 120 % of rated voltage operating time 10 ms nominal at rated voltage.
Definite time delay relay
The type VTT static delay relay is particularly suitable in applications requiring large number of operations and consistent accuracy with little of no maintenance overlong periods. It is also commonly used in industrial processes. A stabilized voltage is applied to a resistance or capacitance circuit and the potential developed across the capacitor is applied to a transistor switching circuit, which operates and attracted armature relay when the potential reaches the triggering level. The time delay is varied by altering the resistance value in the resistance or capacitance circuit by a potentiometer calibrated in se. A circuit to protect the transistors from damage due to high peak transients in supply voltage is incorporated. A diode is also fitted in the circuit to take care of in Advertent connection of supply with the reversed polarity. Type VTT 11 units have a delayed pick up, where as type VTT 12 units have a delayed drop off.
Auxiliary relays
Control, alarm indications and other auxiliary duties in AC or DC system. CAA ;and VAA are current and voltage operated relays respectively. The relays are attracted . armature units of compact design with positive action and high degree of mechanical
stability. The relays can be supplied with self, hand of self and hand reset contacts.
Standards contacts are of silver or copper alloy. They are shaped and positioned to ensure a f reliable and low resistance normally open or normally closed contact.
Negative sequence over current relay
Relay type MCND 04 is a negative phase sequence over current relay and is intended primarily for the unbalance protection of generator. Unbalanced loads or faults in the system can cause negative sequence currents in stator and this induced double frequency eddy currents in rotor of generator. Heating of the rotor is proportional to its AC . resistance at twice system frequencies and even a modest value of negative sequence current can cause serous over heating.
The purpose of the relay to disconnect the generator before an excessive temperature is reached. In order to avoid unnecessary tripping, the operating time characteristic of the relay must match with the negative sequence withstand characteristics of the generator. The type MCND 04 relay has an adjustable time or current characteristics, which make it suitable for generator of different designs.
Field Failure Relay
The type MYTU 04 relay detects the loss of field supply or reduction in the field current or synchronous generator beyond the stability limits of the machine.
Loss of fields supply to the synchronous generator can be caused by a fault in the field circuit or by incorrect opening of the field circuit breaker. On loss of field, the machine operates as an induction generator excited by reactive power drawn from the system to which is connected. This could result in instability of power is a system and over heating of the rotor, especially if the machine is of the cylindrical rotor type without damping winding in the pole phases. The relay operation is blocked when the value of the input voltage falls below .2Vn or .4Vn to avoid mal operation due to Synchronizing surges and transient conditions, the relay is provided with an inbuilt timer with adjustable setting. The delay may be arranged to initiate alarm or tripping if adverse field conditions persist longer than a safe period. A front plate mounted LED is available to indicate relay operation. A push button is provided for resetting the LED indication.
Operation of the relay can be tested by means of test push button; which causes the comparator to operate and the LED to indicate after the set time delay. The output relay is however prevented from the operating during the test. Access to the test push button "requires removal of the front cover.
Definite time Delayed Voltage Relays
The MVTU range of relays provides definite time voltage protection. The MVTU 13 is a definite time delays neutral displacement relay, which is included primarily for the earth fault protection of alternator stator windings where the neutral is earthed. The relay is designed such that is response to third harmonic frequencies is suppressed, thus making it inoperative to the third harmonic load unbalance which normally flows in the generator neutral The application of the relay also includes protection against unbalanced condition in capacitor banks and the deletion of earth fault in impedance earthed, solidly earthed or unearthed system. The MVTU 18 is a define time delayed neutral displacement relay
Virtually identical to the type MVTU 13 with a second time delay starting after the first has elapsed.
Definite time delayed neutral displacement
The operation this relay is identical to the type MVTU 12, with the following difference; the input circuit ha an additional low pass filter fitted to suppress third harmonic components with a third harmonic rejection ratio of better than 20:1. The voltage setting range is lower on the MVTU-13.
]
Definite time delayed neutral displacement
The operation of this relay if identical to the type MVTU 13 with the following difference: After the first time delay tl has elapsed, the output element RL1 is energized and the second time delay t2 starts. RL2 is then operated after the second time delayt2 has elapsed.
Tripping and Control Relays
BE"1'' ' *
These relays are suitable for use in high security CB tripping circuits. In particular they can be used in distributed tripping or control relays contact logic scheme, where the initiating contact May be remote from the relay. The relays have a high burden, which is either cut off at operation or economized to a low figure, either instantaneously or after a time delay.
The high burden provides immunity to capacitance discharge currents, which can result at the inception of an earth fault on battery wiring and immunity to the subsequent leakage current. The high burden also permits the use of supervision relays such as type MVAX where the wiring is at risk and provides reliable operation of series elements such as repeat relays type MVAJ relays can be provide with a time delayed economizing feature.
Directional Over current relays
KCEG relays include directional elements which can be selectively used to control any over current or earth fault element. These relays may be applied where directionality is required to ensure full operation co-ordination. They are particularly cost effective where both directional and non-directional protection is needed at one point on a power system. Start elements which might be interlocking the high speed element s of adjacent relays, can also be directionalised where necessary. In some applications it may be required to select directionally for the earth fault protection of a KCEG relay. For a resistance-earthed cable power system, where capacitance current may be high in relation to the limited earth fault current, it may be necessary to control earth fault elements with a leading directional element characteristic. This prevents sympathetic operation of healthy circuit earth fault elements in the event of an earth fault on another circuit. When non-directionalised, the KCG over current elements will perform in the same manner as KCEG elements.
Pole Slipping Protection
The KCEG 140 relay is three phase over current and earth fault relay. The relay uses a common measuring element for all3 phases and a separate element to monitor the residual current. The phase volt settings and earth fault settings are completely separate. Both the phase fault element and the earth fault element have 3 tripping stages, which can be enabled and disabled as required. The relay also features an alternating setting group, in which 3 tripping stages for both the phase over current and earth fault element can be enabled or disabled differently to that implemented with the first setting group. The relay has programmable output relay and opt-isolated digital inputs.
Rotor Earth Fault Protection Relay
The type DBAE relay is applied to detect each leakage in alternator field circuits which are fully isolated from earth. It is suitable for use with thyristors excitation system.
The auxiliary AC bias supply is rectified to establish a small bias on alternator field circuits so that all points are negative with respect to earth. In the event of earth leakage current flows in the bias circuit and is detected by the sensitive Db coil as additional safe guard, the relay functions as a self powered rotor earth fault relay in the absence of the injection supply, effectively covering a large protection of the field winding; the actual protection covered depends upon the ratio of field voltage to relay rated voltage and may be high as 95 %. The external resistance, supposed with the relay limits the fault current flowing in the DB coil.
Digital definite time frequency relay
They type MFVU 14 frequency relay consist of 2 independent frequency monitoring circuit, one for unit and other for over frequency measurement. Relay operation is blocked when there is an abnormal fall of the monitored voltage to less than 40 % of rated value.
The relay is suitable for any application in Industrial plants and for generators where definite time under or over frequency protection is required. In addition, multi stage schemes using several relays can be provided for load shedding and reconnection applications. Integral timers are provided for each operating circuit and a separate electromagnetic auxiliary relay ensures maximum flexibility of applications.
Voltage selection Relay
MVAP 22 is essentially a fuse failure relay with change over output contact enabling its use for either voltage selection or fuse failure protection. A typical application as a voltage selection relay is the automatic connection of the metering equipments to an alternative supply if the normal or the perfect supply fails. As a fuse failure relay it will monitor the out put of a voltage transformer and give an alarm or disconnect protection circuit for VT fuse failure.
The relay monitors the three phase voltage supply and if the supply is interrupted or becomes unbalanced due to the failure of the voltage transformers primary or secondary fuses.
Forward and reverse power Relay
The MWTU 11 is suitable for the following applications. Reverse power protection of a generator against motoring
The relay has sensitive settings and operates accurately for boundary conditions up to +/_ 87.10 (0.05 pf). The definite time characteristics ensures that mal operations does not Occur due to momentary power reversals during synchronizing or power swings on the system.
I Limitations of Power imported from a consumer by a Utility Power Supply
This application is an over power or forward power functions in which higher settings are required. The directional discrimination is not required at such low pf for reactive . components as high as 60 % of the generator rating. The operating time of the relay is not critical as fast tripping times are covered by fault detecting relays.
Over current for phase and earth faults
The relay can be used in applications where time graded over current and earth fault operation is required. The relay can be used to provide selective protection for over head and under ground distribution feeders. Other applications include backup protection for transformers, generators, and HV feeder circuits and protection of neutral earthing resisters.
High stability circulating current relay
When circulating current protection schemes are subjected to heavy through faults, the student, and often asymmetrical growth in the system current can cause the protective current transformer to approach or even reach saturating level. Because of the variations in the magnetizing characteristics of the transformer a high unbalance current may result to ensure stability under the condition, it is modern practice to use a voltage operated, high impedance relay to set to operate at a voltage slightly higher than that developed by the current transformer under maximum external fault conditions. The MCAG14 relay , used for applications where sensitive settings with stability on heavy through faults are required, and is recommended for balanced and restricted earth fault, bus zone and certain forms of differential protection for transformers, reactors and motors.
Voltage dependent over current relay
For back up over current protection of generators ordinary over current relays are some times difficult to apply, due to the decaying characteristics of the fault current. The value of the fault current will be progressively reduced due to the reaction, to a value less than full load current. Therefore, normal over current relays, set above the load current or maximum permissible overload cannot be applied to provide time delayed protection as they will not operate for therefore fault conditions. For successful application of generators backup protection, the relay is required to be a function of voltage and current. There are two types of relays that are customarily used for these applications, namely voltage restrained and voltage controlled over current relays with voltage restrained over current relays, when the voltage falls below a set values, the operating time of the over current characteristics is continuously reduced with declining voltage. In voltage controlled over current relays, the operating time characteristics are changed from the load characteristics to the fault characteristics when voltage falls below the set level. The MCVG61 is a 3phase voltage dependent over current relay with both voltage restrained and voltage controlled characteristics available from the same relay. A switch on the front panel of the relay selects the desired mode.
NUMERICAL RELAYS
Medium-sized and large generators make a major contribution to power generation. They carry the basic load and ensure the stability of an energy system. The task of electrical protection in these systems is to detect deviations from the normal condition and to react according to the protection concept and the setting. The scope of protection must be in reasonable relation to the total system costs and the importance of the system.
In medium-sized and large power stations the generators are operated exclusively in unit connection. In the unit connection the generator is linked to the bus bar of the higher voltage level via a transformer.
In the case of several parallel units, the generators are electrically isolated by the transformers. A circuit-breaker can be connected between the generator and the transformer
Numerous protection functions are necessary for reliable protection of electrical generators. The scope and the combination are determined by various factors such as generator size, operating principle, system design, availability requirements, experiences and philosophies. This automatically leads to a multi-functionality which can be controlled excellently by numerical technology.
High-performance protective relaying comes into its own when it's a question of minimizing power system operating costs. Uncomplicated operation, convenient commissioning tools and flexible communication are all important elements when service and maintenance costs have to be reduced. These relays not only handle fault detection and location tasks but also control, metering and monitoring functions. And it is these additional functions - impossible before the advent of numerical technology - which offer major cost-cutting potential.
The SIPROTEC 4 relay family offers fully integrated protection, control, monitoring, and automation functions incorporated in a single device. For many applications, this product contains all the functions you need to meet all your protection and Control requirements with Just one unit per bay, saving on investment and Installation costs and enhancing availability.DIGSI 4 - one tool for all tasks and Products DIGSI 4 is a computer program designed for all SIPROTEC relays.
DIGSI 4 offers users a universal tool for all support tasks from setting and commissioning of devices to simple analysis and documentation of system faults. Our powerful analysis tool speeds up troubleshooting and supplies important service information.
NUMERICAL RELAY-OVERALL PROTECTION
The SIPROTEC 4 type relays are numerical, multifunctional, and protective and control devices equipped with a powerful microprocessor. All tasks such as acquisition of the measured quantities issuing of commands to CBs and other primary power system equipment are processed in a completely digital way. Figure shows the basic structure of the device.
Analog Inputs
Measuring inputs (MI) selection consists of current and voltage transformers. They convert he signals from the measuring transducers to levels appropriate for the internal processing of the device. Four current inputs are available in the MI section. These inputs are used for measuring of the phase currents. The use of the forth current depends on the version of the device ordered. The forth input can be used for measuring the ground current as the residual of the phase current of the transformers, or for measuring the ground current from a separate current transformer. The latter is used in a highly sensitive ground fault protective scheme or a polarizing current to determine the fault direction. The four voltage transformers of relay can either be applied for the input of 3 phase ground voltages, one displacement voltage or a further voltage for the synchronizing function. The analog input quantities from the MI stage are passed on to the input amplification (IA) stage, which provides high resistance termination for the analog quantities. The IA stage consists of filters for processing in the measured values. The filters are optimized with regard to band width and processing speed. The analog to digital stage (AD) consist of memory components, a multiplexer and an analog to digital (A/D) converter. The A/D converter processes the analog signals from the IA stage. The digital signals from the converter are input to the microcomputer system where there are processed as numerical values in the residing algorithms.
Micro computer System
The protection and control functions of the numerical relays are processed in the microcomputer system. In addition, the microcomputer controls the measured quantity specifically, the microcomputer performs:
Filtering and preparation of the measured quantities.
Continuous monitoring of the measured quantities.
Monitoring of the pickup conditions for the individual elements and functions.
Evaluation of limit values and sequences in time.
Control signals for the logic functions.
Decision of trip, close and other control commands.
Output of control commands for switching devices.
Recording of messages and data for events, alarms, faults, control actions and provision of their data for analysis.
Management of the operating system and the associated functions such as data Recording, real time clock, communication, interfaces etc
Binary Inputs and Outputs
The microcomputer obtains external information through the binary inputs such as blocking commands for protective elements or position indications of CB. The microcomputer issues commands to external equipments via output contacts. These output commands are generally used to operate CBs or other switching devices. They can also be connected to other protective devices, annunciators, or external carrier equipments for use in pilot relaying schemes.
Front Elements
The devices with integrated or detached operator panel light emitting diodes (LED) and displays screen (LCD) on the front panel providing information such as messages related to events and functional status of the device.
The integrated control and numerical keys in conjunction with the LCD facilitates local operation with the numerical relay. All information of the device can be accessed using the integrated control and numerical keys. The information includes protective and a Control, settings operating and fault messages and metering values. The settings can be modified; in addition control of CB and other equipment is possible from the front panel.
Serial Interfaces
A serial PC port on device is provided for local communication with the relay through a personnel computer. Convenient operation of all functions of the device is possible. The operating system which facilitates a comfortable handling of all devices functions.
A Separate service port can be provided for remote communication in a modem or substation computer. The operating program is required. The port is especially well suited for the fixed wiring
Of the devices to the PC or operation via a modem. The service port can also be used to connect a RTD-Box for entering external temperature (e.g. for overload protection). The additional port is exclusively designed for the connection of a RTD-Box for entering external temperature.
All relay data can be transferred to a central control and monitor system through the SCADA port. Various protocols and physical interfaces are available to suit the particular operation.
A further port is provided for the time synchronization of the internal clock via external synchronization sources.
Further communications protocols can be realized via additional interface modules.
Power Supply
The relay can be supplied with any of the common power supply voltages from 24v DC to 250V DC. The device can also be supplied with 115 V AC. Momentary dips of the supply voltage up to 50ms are bridged by a capacitor. Voltage dips can occur for example, of the voltage supply system becomes short-circuited or experiences a source variation is load. .
INTERNAL ARCHITECTURE OF NUMERICAL RELAY
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APPLICATIONS
The numerical, multifunctional SIPROTEC 4 relay is versatile devices designed for many applications. The relay can be used as a protective, control, and monitoring devices for distribution feeders and transmission lines any voltage in networks that are grounded, or of a compensated neutral point structures, the devices are suited for networks that are radial or looped, and for lines in single or multi terminal feeds; the relay are equipped with motor protection available for asynchronous machine of all sizes.
The relay includes the functions that are necessary for protection, monitoring of circuit breaker position, and control of the circuit breaker in straight bus application or breaker and a half configuration; therefore, the devices can be inversely employed. The relay provides excellent backup facilities of differential protective scheme of lines, transformers. Generators, motors, and bus bars of all voltages
A. Protective Functions
Non-directional over current protection is the basis of the numerical relay. Four definite over current protective elements exists, two for he phase and two for ground current. The elements can set with time delay, where instantaneous tripping is decide inverse time over current protective elements are also available for both the phase and ground currents. The common US ANSI time characteristics are also available, alternatively user defined characteristics can be programmed or IEC characteristics can be selected.
Depending on the version of the device that is used, the non directional over current protection can be supplemented with directional over current protection, breaker failure protection, and sensitive ground fault detection for high resistance ground fault or system data's are resistively ground. The highly sensitive ground fault detection can be directional or non directional include negative sequence current protection, automatic reclosing,. thermal overload protection, over voltage protection, under voltage protection, and over/under frequency protection. For another port, starts inhibit, and under current monitoring are optionally available. Finally the relay is equipped with a fault locater.
A port feature can be ordered for the detection of intermittent ground fault which detects and accumulate transient ground fault.
External detectors account for ambient temperature or coolant temperature (By means of an external RTD box)
Before reclosing after 3 pole tripping, relay can verify the validity of the re-closure by voltage check and/or synchronous check. The sign function can also be controlled externally
B. Control Functions
The relay supports all control monitoring functions that are required for operating medium to high voltage substation. Major applications are the reliable control of switch gear or CBs. Such control can be accomplished via the integrated operation panel, the system interface, the binary inputs and the serial ort using a personnel computer with DIGSI. .
The status of the equipment or auxiliary devices can be transmitted to the relay via auxiliary contacts connected to the binary input. The present status or the position of the primary equipment can be displayed on the relay. And used for interlocking or, is applicable, possibility monitoring. Only the quantity of the binary input and output available in the numerical relay limits the no of primary devise that can be operated. Depending on he equipment being controlled, I binary input or 2 binary input can be used in the position monitoring process.
The capability of switching primary equipment can be restricted by a setting associated with switching authority-local, DIGSI 4, or remote, and by the operating mode interlocks or non-interlocked, wit password request. Processing of interlocking condition for switching (e.g. switching error protection can be established with the aid of integrated, user configurable logic function.
C. Messages and Measured Values; Recording of Event and Fault
data
The operating message provides information about condition in the power system and the relay. Measurement quantities and values that are calculated can be displayed locally and communicated via the serial interfaces.
Messages of the relay can be indicated via a no of programmable LED s of the front panel, externally processed through programmable output contacts and communicated via the serial interface.
Important events and changes in condition are saved under annunciations in the event Log or the Trip Log, the later being used for the faults. Waveforms capture is available as an option.
D. Communication
Serial interfaces are available for communication with PCs, RTU s and SCADA systems.
A 9 pin D-subminiature female connector on the front panel is used for local communication with a personnel computer. DIGSI 4 software is required to communicate via this port. Using the DIGSI 4 software, settings and configuration can be made to the relay, real-time operating quantities can be viewed, waveform capture and event by records can be displayed, and controls can be issued.
A DIGSI 4 service interface port a system (SCADA) port and a time-synchronize port are optionally available on the rear o the device.
A rear service interface can be supplied as RS-232, RS-485 or multimode fiber optics type ST. DIGSI 4 software is required to communicate via this port.
This additional port is designed exclusively for connection of RTD-Box for entering external temperature. It can also be operated via data lines or fiber optic cables.
A rear system interface can be supplied as RS-232, RS-485 or multimode fiber optics type ST for communication s between the relay and PCs RTU s or SCADA systems standard protocols, IEC 60870-5-103 are available via the system port. Integration of the Device into the automation systems SINAUT LSA and SICAM also take place with this profile.
Alternatively, a field's bus coupling with PROFIBUS FMS is available for the relay. The PROFIBUS FMS is performed in accordance with IEC 61850, is an open communication standard that particularly has wide acceptance in process control and automation engineering, with especially high performance. A profile has been defined for the PROFIBUS communication that covers all of the information type required for protective and process control engineering. The integration of the device into the energy automation system SICAM cab also take place with this profile.
Besides their field-bus connection with PROFIBUS FMS, further couplings are possible with PROFIBUS DP and the protocols DNP3.0 and MODBUS. These protocols do not support all possibilities which are offered by PROFIBUS FMS.
CHARACTERISTICS
General Characteristics
Powerful 32 bit microprocessor system
Complete digital processing and control of measured values, from the sampling of the analog input quantities to the initiation of outputs for, as example, tripping or closing circuit breakers or other switch gear devices
Total electrical separation between the processing stages of the relay and the external transformer circuits, control circuits and DC supply circuit because of the design of the binary inputs, outputs and the DC Converters
Complete set of functions necessary for the proper protection of lines, feeders, motors and bus bars
Easy device operation through an integrated operator panel or by means of connected personnel computer running DIGSI 4
Continuous calculation and display of measured quantities on the front of the device
Storage of Min/Max measured values and storage of long term mean values
Recording of event data, fault data, and waveform capture with SER information to be used for analysis and trouble shooting
; Constant monitoring of the measured quantities, as well as continuous self diagnostics covering the hardware and software
Communication with SCADA or substation controller equipment via serial interfaces through the choice of data cable, modem or optical fibers
Battery buffered clock that can be synchronized with an IRIG-B signal. Binary input signal, or system interface command
Recording of CB statistics including the number of trip signals sent and the accumulated, interrupted currents of each pole of the CB
Tracking of operating hours of the equipment being protected
Commissioning aids such as connection check, direction determination, status indication of all binary inputs/outputs and display of test recordings.
Time over current protection
Two instantaneous 9Definite time) over current elements and inverse time over current element, for he phase protection and ground protection
The 50 and 50N elements can be set with definite time delay
Common ANSI and IEC time over current curves are available 51 and 5IN, or user defined characteristics can be employed
Blocking capability for reverse-interlocking bus bar protection, or directional comparison line protection
Second harmonic inrush restraint of 50, 50N, 51 and 5 IN for transformer energizing
Instantaneous tripping by any over current element upon manual closure of a CB, if selected (Switch-onto-fault-protection)
Directional Time over Current Protection
The directional time over current elements for both phase protection and ground protection .The 67 and 677N elements can have instantaneous or definite time tripping. The -TOC and 67N-TOC elements have inverse time characteristics. The Directional times over current elements are independent of the non-directional time over current elements
Fault direction is calculated for each phase and directions determined independently for phase faults and for ground faults
Dynamic cold load setting adjustment
Dynamic adjustments of the pick up and the tripping time of both the directional and non directional time over current functions where cold load conditions are anticipated
Cold load conditions are anticipated when the CB has been in the operation in the open position for an extended period of time. CB Position is determined by auxiliary contacts or the state of a sensitive over current element
Activation via automatic re-closure (AR) possible
Start also possible via binary input
Voltage Protection
Two under voltage elements 27-1 and 27-2 measuring positive sequence voltage
Choice of current supervision for 27-1 and 27-2
Adjustable drop out voltage for 27-1
Separate over voltage elements 59-1 and 59-2
Negative sequence current protection
Two definite-time elements 46-1 and 46-2 and one inverse time element 46-TOC
Common US ANSI time characteristics or IEC characteristics are available for 46-TOC
Frequency protection
Four elements that are independently adjustable for function-under frequency or over frequency pick up and time delay
Sensitive to harmonics and abrupt phase angle changes
Adjustable under voltage blocking
Thermal over load protection
Temperature rise of the protected equipment is calculated during a thermal homogenous body model that takes into account energy entering the equipment an energy losses. Thermal over load protection has full memory capability
2 RMS calculations
Adjustable warning level base don temperature rise and current magnitude
Additional constant setting for motors to accommodate both the motor rotating and the motor at stand still
Integration of ambient temperature or coolant temperature is possible via external temperature sensors and RTD-Boxes
Monitoring Function
Availability of the relay is greatly increased because of self monitoring of the internal . measurement circuits power supply, hardware and software
Current transformer and voltage transformer secondary circuits are monitored using summation and symmetry check techniques
Trip circuit monitoring
Phase rotation
Sensitive ground fault protection
Ideal for sensing a grounded phase on ungrounded networks
Displacement voltage is calculated from the measurement of three phase ground voltages, or measured from the output of, for e.g., voltage transformers connected in an open delta configuration
Ground fault detection optionally with high sensitivity or for large current
Two sensitive ground faults instantaneous over current elements 50NS-1 and 50NS-2 are adjustable and can be set very sensitive as low as 10mA)
Sensitive ground fault time over current element 5 INS is available instead of 50NS-1, if selected
Time-current characteristics curve for 5 INS is defined by the use
Two ground fault elements 67NS-1 and 67NS-2 that can be set as non-directional forward sensing directional or reverse sensing directional
Fault direction is determined by calculating the zero sequence real power or reactive power as determined by a setting
Directional characteristics of 67NS-1 and 67NS-2 are adjustable
Optionally application as additional ground fault protection
Intermittent Ground Fault Protection
Detects and accumulates intermittent ground fault.
Tripping after configurable total time.
Automatic Enclosing
Single shot or multi shot.
Dead times associated with the first, second, third, and fourth shots are programmable and can be different fro, one another. Dead times for the remaining shots are identical to the dead time for the forth shot.
Protective elements that initiate automatic reclosing are selectable. The choices can be different for phase faults and ground faults.
Different programs for phase and ground faults.
Monitoring of the CB response during reclosing sequence is possible.
Interaction to the time over current protection stages and ground fault stages. They can be blocked in dependence of the enclosing cycle or released instantaneously.
Synchronous reclosing is possible in continuation with the integrated synchronizing . feature. .
Fault Location
Triggers includes a trip command, rest of their trip command, operation of a protective element and an ext command via a binary input;
Fault distance is calculated and given in secondary ohms, miles, or kilometers.
Breaker Failure Protection
Breaker failure condition determined by current flow and or evaluation of circuit breaker auxiliary contacts after a trip signal has been issued.
Breaker failure protection initiated by the tripping of any integrated protective element that trips the CB
Initiation possible through a binary input fro an external protection device.
Initiation possible through the integrator control function.
Synchronizing Function
Verification of the synchronizing condition before reclosing after 3 pole tripping.
Fast measurement of voltage difference AU, the angle difference and the frequency difference
Alternatively, check of the de energized state before reclosing.
Switching possible for asynchronizing condition with production of the synchronizing time
Settable minimum and maximum voltage
Verification of synchronizing condition of de-energized state also possible before the manual closing of the CB with separate values
Measurement also possible via transformers with out without external intermediate matching transformer
Measuring voltage optionally phase to phase or phase to ground.
RTD-Boxes
Detection