Transformer protection

Transformer bay — one device, multiple roles

A transformer bay rarely needs a single protection function. Depending on transformer size, vector group, neutral treatment and the number of CT groups, the protection device must cover differential (87T), restricted earth fault (REF), overcurrent on both sides, and thermal/Buchholz signals from the transformer itself.

SYMAP^® Y-T1/T2/T3 are dedicated transformer variants scaled by the number of CT groups. Compact+ (+F3/+F4) with the 87 option covers transformer bays in compact switchgear, where the same device also manages HV/LV breaker control and interlocking.

Typical transformer applications

Power transformers

HV/MV power transformers in transmission and distribution substations. Full 87T differential with magnetizing-inrush restraint, REF, overcurrent, overload, frequency.

Generator step-up transformers

Block transformers connecting generators to the grid in hydropower, CHP and thermal plants. Integration with generator protection (SYMAP^® Y-G or BCG) for combined block protection.

Distribution transformers

MV/LV distribution transformers in industrial plants, urban substations and commercial buildings. Overcurrent, earth-fault and thermal protection with HV breaker control.

Marine and offshore transformers

Shore-power transformers, propulsion transformers, auxiliary distribution. Type approvals from leading class societies (LR, ABS, DNV, BV, CCS, PRS, NK, RINA, KR).

Auto-transformers

Auto-transformers in transmission substations and motor starting applications. Specialised CT configurations and tap-changer monitoring.

Retrofit transformer protection

Compact+ or classic SYMAP^®?

Classic SYMAP^® Y-T1/T2/T3 covers transformer applications with 87T differential (T2/T3) and REF protection scaled to the number of CT groups. SYMAP^® Compact+ (+F3/+F4 with 87 OPTION) applies where the transformer sits in a compact switchgear panel with HV/LV breaker control.

Products covering the transformer application

Need detailed technical specifications?

For exact protection function coverage, settings ranges, ANSI device numbers, CT/VT specifications, communication protocols and configuration support, contact our team to receive the relevant datasheet and engineering proposal.

Request datasheet Engineering inquiry