Bushing failures are considered as one of the significant causes of transformer outages. Historically bushings were tested offline to measure the capacitance and the dissipation/power factor (tan delta).
The bushing monitoring system, which has been developed in cooperation with ZTZ Services, incorporates three measurement modes for standard and two for optional configurations:
Standard configuration with 6 current inputs:
- Sum of three current tests
- Adjacent phase reference test
- Phase comparison
Optional configuration with 3 voltage and 3 current inputs:
- Reference test (3 bushings and 3 CCVT`s)
Optional configuration with 6 voltage inputs:
- CCVT Reference test (6 CCVT`s)
The bushing sensors/adapters are connected to the capacitor taps designed for all bushings to measure the leakage current up to 140 mA AC.
The adapters are designed for bushings with grounded and undergrounded capacitor taps. The adapter is designed to prevent voltage from developing on the equipment when the sensor becomes disconnected from the bushing monitoring system.
The Bushing Monitor ZVCM-1001 communicates directly with HYDROCAL 1005 and 1008 units and in conjunction with these units, it offers a complete transformer and bushing monitoring system.
- Simultaneous measurement of up to six bushing leakage currents, providing following data:
- Relative capacitance in percentage to the start-up value
- Relative power factor (%PF) for each bushing
- Magnitude of imbalance currents for two three-phase sets of bushings
- Phase angles of the imbalance currents
- Alarm in case the measured values exceed the threshold
- Complete on-line transformer monitoring and bushing monitoring system in conjunction with HYDROCAL 1005 and 1008
The bushing monitoring system ZVCM-1001-3E connects to Hydrocal 1004 genX, 1005, 1005 Offshore, 1008, 1008 Offshore, 1009, 1009 Offshore via an RS-232 interface. The system consists of:
- 3 bushing sensors type VBS-1 YG with connection cable
- Bushing Monitor ZVCM-1001 including mounting plate, power supply, circuit breaker, terminals and wiring
- HYDROCAL communication cable (10 or 15 m)