PCS-9671 three winding power Transformer Differential Protection Relay Microprocessor

PCS-9671 three winding power Transformer Differential Protection Relay Microprocessor  Restraint current differential protection. (87T),   CT saturation detection

The PCS-9671 is a microprocessor-based relay designed for the protection of two-winding or three-winding power transformers with maximum three CT inputs. It also can be used to protect reactors or applied as an stub differential protection. The restraint current differential protection, unrestraint differential protection and restricted earth fault protection are provided.

The relay is capable of sampling the analog signals from conventional transformers, or receiving the sampled values from electronic CTs/VTs via merging units. The programmable logic, LEDs, binary inputs and outputs can be configured according to the specific requirements through software tool. It provides the interfaces for station bus and process bus respectively and supports IEC 61850-8-1 MMS, GOOSE, IEC 61850-9-2 Sampling Value.

Protection and Control
 Restraint current differential protection. (87T)

Two stages with low-setting and high-setting are provided for this protection. And the low-setting stage could be blocked by CT saturation, inrush current, overexcitation and CT circuit failure. As well the high-setting stage could be blocked by inrush current and CT circuit failure.

Unrestraint current differential protection. (50/87UT)It is used to clear the serious internal fault quickly.

 Restricted earth fault protection. (REF)

Up to 3 REF protections based on zero-sequence current differential element are provided.

Phase overcurrent protection for each side.(50/51P)

Up to 3 overcurrent protections are provided.

 Mechanical protection. (MT)

Up to 8 mechanical channels are provided.

 CT circuit supervision. (CTS)

CT circuit supervision consists of two elements: CT circuit abnormality without fault detector pickup and CT circuit failure with fault detector pickup.

 Inrush current blocking by 2nd harmonic

Phase-segregated blocking, cross blocking and composited blocking are provided for selection.

 Overexcitation blocking by 5th harmonic

Overexcitation is detected via the ratio of 5th harmonic current and fundamental current.

 CT saturation detection

CT saturation is distinguished via composited 2nd and 3rd harmonics.

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PCS-9671 three winding power Transformer Differential Protection Relay Microprocessor