INVERSE TIME NUMERICAL CURRENT RELAY WITH COMMUNICATION
Product Code: JNC 068CALPS
Time line :Products will be shipped within 3 weeks from the date of order
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- Programmable CT secondary current for 1A / 5A rating
- Programmable system rated frequency (50/60Hz)
- Display of Primary current
- Available in many variants to suite main and back-up over-current protection schemes
- Available in both Low load and normal load configurations
- Choice of 6 IDMT curves and definite time with hi-set (two stage characteristics)
- Cold load pick-up
- MIPConS for preventing E/F element operation during single-phasing
- Trip Coil Supervision Relay
- Multi-short auto re-closer facility
- Self supervision facility
- Trip test facility
- History of 200 latest comprehensive fault records along with settings
- Latest 100 event records can be stored
- IEEE COMTRADE compliant disturbance records
- MODBUS open protocol over RS – 485 port
- MODBUS protocol over RS – 232 port
- Draw-out facility with inbuilt CT shorting
- Standard dimension – 144mm x 144mm
- History of 200 latest comprehensive fault
The relay provides time graded phase and earth fault (2 stage) protection, (high impedance) restricted earth fault protection. MODBUS communication protocol over RS-485 facilitates interfacing the relay with SCADA systems and RS – 232 communication port provided at the front of the relay allows engineers to program the relay with ease. Certain advanced features such as “Cold load pickup” and MIPConS improves the sensitivity, stability and availability of the system.
PRINCIPLE OF OPERATION
Over current relaying principles
The relay measures the line current from each of the line CTs and if the current exceeds the set threshold, then relay extends a trip signal after an operating time. The relay's “operating time” is determined by selecting “definite time” or one of the six “inverse time” characteristics. This principle of relaying is equally applicable to both line and earth fault protection elements (51N / 51G).
Cold load pick-up
This feature can be useful in providing better selectivity in the operation of over current relays, by preventing them from operating, during inrush phenomenon.
MIPConS - Management of Imbalance Phasor Control through Supervision
Under the existing practice of operating the distribution network in 2-phase mode (popularly known as single- phasing)for certain strategic purposes, conventional earth fault relays in substa- tions would pick-up and trip the circuit breaker. This operation is considered by the engineers as an undesirable outcome of a planned current un-balance in the system. “MIPConS”, when enabled, automatically detects the single-phasing operation and restoration of 3-phase system. Consequently, the feature prevents “earth fault element” from extending trip command under single-phasing conditions.
Trip Test Facility
The trip test will facilitate testing of relay operation without applying the input current. The trip test is useful to test the panel wiring and operation of breaker without any current. The trip contact will operate instantaneously. The phase and earth fault alarm contact will not operated during the trip test.
Restricted earth fault protection
A simple earth fault protection may not provide adequate protection for transformer windings particularly when in the case of "Y" connected winding earthed with an impedance. The efficacy of protection is improved by employing restricted earth fault protection. The said protection scheme is prevalent even under the case of “solidly earthed systems”. High-impedance protection scheme requires the residual current derived from the three line CTs to be balanced with the "neutral current" derived out of neutral CT. This unit protection scheme is generally sensitive only to the fundamental harmonic component of the measured current and has an "instantaneous time" as its operating characteristics.
Auto re-close facility
Relay has a multi shot auto re-closer facilitates automation for breaker operation. Auto re-closer can be programmed to provide a maximum of five shots. “Dead time” starts when a trip signal is provided due to the occurrence of a fault involving L-L or L-G or L-L-G or L-L-L or L-L-L-G. After an elapse of a time interval equal to “dead time”, closing command will be extended. The “reclaim time” timer starts at the instant when the “dead time” timer expires. If after extending the “breaker close” signal an over current fault was detected before the “reclaim time” timer reached its terminal count, then the relay understands that the fault in the system is still persisting and the over current relay will issue a trip signal. The relay tries to close the breaker for a maximum of the programmed number of shots before it chooses to lockout. The relay can be configured for independent trip sequence as IDMT or Definite time.
TCSR monitors trip coil continuously. If the trip circuit (or any coil) that is being supervised develops a snag, then the supervision relay extends an alarm without a delay. The relay monitors the trip coil under all the states of a breaker viz. close, open and during transition. The underlying mechanism of supervision is to perform hi- impedance measurement across two input circuits appropriately wired along with trip coil, 52A and 52B auxiliary contacts. 1-NO & 1-NC contacts have been provided for the purpose of alarm and SCADA. The current rating of these contacts is 5A at 24VDC / 230VAC.
Self supervision feature allows the operator to take note of any internal failure in the relay. An LED and an output contact is provided for annunciation purposes.