In order to work properly, protection and control systems have to be correctly integrated into the substation or power plant. Quantities from the primary system are transformed at the VTs and CTs – using their different cores – and so the voltage and current signals must be correctly connected to the protection relays, automation units and meters.
From these protection and control units, the trip signals are routed back to the primary apparatus, for example, the circuit breakers. A fault in any part of this system may result in a system failure – false tripping or a failure to trip.
To prevent such a failure, the system’s functionality can be verified by injecting into the primary side of the CT or VT and checking the measured values at the relay or automation unit. Finally, injecting current at the magnitude of a fault should result in the tripping of the circuit breaker, which allows the verification of the complete chain.
The Omicron CPC 100 Multi-functional Primary Test System allows the verification of the ratio and polarity of CTs and VTs – preventing wrong connections, especially in the case of tapped CTs. Injecting current or voltage into individual CTs / VTs and checking the reading at the relay ensures that phases are not mixed up and that the CT and VT ratio setting in the relay is correct.
The CPC 100 can also measure the burden on the CTs and VTs and, by determining the CT’s excitation curve, it ensures that the protection circuits are connected to the appropriate CT cores.
The CPC 100 can help to verify that the secondary wiring is correct. By injecting a sawtooth signal into the CT or VT, the operator verifies with a handheld device that the signal has the correct polarity at the connection points of the secondary systems.
With the CPC 100 primary faults can be simulated to check if overcurrent, differential or distance relays operate correctly. The total trip time including the CB operating time can also be measured in this test.
Protection installation testing
• CT ratio (with burden) up to 800 A or 2000 A with the CP CB2, 5 kVA output power
• CT burden up to 6 AAC | secondary
• CT excitation curve (knee point) up to 2 kVAC
• VT ratio up to 2 kVAC | polarity and burden
• VT burden up to 130 VAC | secondary
• Overcurrent relays with primary injection (MV) up to 800 A or 2000 A with the CP CB2, 5 kVA output power
• Polarity check with CPOL up to 800 A or 2 kVAC, 5 kVA output power
• Testing of the entire protection chain by primary fault current injection and live CB tripping
This is part of the Omicron CPC 100 All-In-One Test System Series. Check out the other posts!