Rotor E/F Protection - ABB REG316 4 Series Operating Instructions Manual

REG 316*4 1MRB520049-Uen / Rev. F
3.5.11.2.

Rotor E/F protection

Settings:
Overvoltage
Delay
Over/undervoltage
The rotor E/F function in conjunction with the ancillary unit Type
YWX 111 and 2 coupling capacitors is suitable for protecting
synchronous generators regardless of the method of excitation.
The scheme operates according to the Wheatstone bridge
principle and is uninfluenced by frequency. The harmonics of the
excitation system do not therefore effect the rotor E/F protection.
The bridge is connected to the rotor circuit by one or two high-
voltage capacitors. The first leg of the bridge consists of the
coupling capacitors and the capacitance of the rotor winding in
series. The second capacitive leg, the resistive legs and a supply
transformer for stepping down the v.t. voltage (e.g. 100 V) to the
50 V needed for the measuring circuit are in the ancillary unit
Type YWX 111. A second transformer isolates the bridge from
the input of the E/F protection function.
An E/F short-circuits the capacitance of the rotor winding and the
bridge is no longer balanced. There is thus a voltage across the
bridge that is detected by the overvoltage function. Depending
on the design of the scheme, the pick-up setting is between 0.5
and 3 V to detect an insulation leakage of 1 k W which is
considered as being a rotor E/F. Since all the components
influence the setting, it is determined during commissioning.
Typical settings:
V-Setting (for 1 k W )
Delay
MaxMin
ABB Switzerland Ltd
V-Setting
Delay
Max Min
1 to 3 V
1 s
MAX
3-135