A NSI codes 27, 59, 78, 81 >G59 protection relay package
Type G59 package >
4921240217D Combined vector shift and ROCOF >
(df/dt) Protection of over-/underfrequency 3 phase protection of over-/undervoltage Digital data processing Fast decoupling of the generator Ensures no as y nchronous reconnection >
G59 package Application >
The mains decoupling relay - type G59 package - forms part of a complete DEIF series of relays for the protec-tion and control of generators. This package is applied for the protection of synchronous generators, running in parallel with the mains. The package protects against over-/under- frequency, over-/undervoltage, vector shift and/or ROCOF (rate of change of frequency, df/dt). In applications with only vector shift or ROCOF, the set point for the unwanted part is set at maximum and this part is hereby disabled. A mains failure will be detected, provided a disconnec-tion at an arbitrary point of the network results in a swift change of the generator frequency. An opening signal is then transmitted to the mains circuit breaker, and the generator will then be protected against damage caused by an automatic reconnection to the high-voltage network. On the other hand, the vector shift/ROCOF will not detect the relatively slow and acceptable changes of the network frequency (the mains). Frequency and voltage protection is needed to protect loads against unacceptable voltages and frequencies. Furthermore, separating the generator from the mains in case of mains failure is also stipulated as a condition in most national rules for connection of synchronous generators to the mains. Measuring principle Relay outputs >
A/S ROCOF, vector shift and frequency measure the voltage between 2 phases or between one phase and neutral. High measuring accuracy is achieved by digital data processing. The ROCOF supervises the frequency change for every period. If the frequency change exceeds the set point for four periods in a row, the ROCOF has detected a failure.
The vector shift supervises the angular velocity of the mains by comparing the times for the latest two full cycles (1st, 2nd) with the times for the full cycles of the previous 4th and 5th period. If the vector shift or the ROCOF detects a failure, an opening signal is transmitted to the mains circuit breaker, and the LED marked MAINS FAILӔ is lit. The over-/underfrequency supervise the frequency by supervising the latest 4 periods. If the under- or over-frequency set point is exceeded, the output is activated and the associated red LED is lit. The over-/undervoltage part measures all 3 phase voltages. If the voltage drops below the set point or exceeds the upper set point, the associated output is activated and the associated red LED is lit. The vector shift and the ROCOF are provided with 1 reset input connected to contacts to the generator circuit breaker and to the mains circuit breaker. These 2 contacts close when the respective circuit breaker is opened. When RESET (22-23) is activated, the vector shift and the ROCOF part will not detect a possible mains failure. This function ensures that the relay is only active when both circuit breakers are closed and the generator is thus running in parallel with the mains. The vector shift and the ROCOF are provided with an initialising timer, which is activated when cancelling the reset signal (closing of circuit breakers). When this timer expires, the vector shift and the ROCOF are activated and the LED SUPERVISIONӔ is lit. The time delay is fixed at 5s. The package is provided with 4 outputs either normally energised or normally de-energised. The contacts may be set to open or to close on activation. Power-up circuit F The relays are provided with a 200 ms power-up circuit, ensuring the correct function of the relay on connection of the auxiliary voltage. DEI size="-3">