Manual 37352A
MFR 12 Packages - Protection Relay
© Woodward
Page 7/62
Measured Value Logging
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
Voltage
Package 51V
: Voltage dependent time-overcurrent.
Current
Packages CP
/
51V
: Three-phase measurement of the r.m.s. value.
•
../1 A ................................[1]
•
../5 A ................................[5]
Ground Fault
The displayed ground current is digitally filtered from the measured currents. This prevents inaccurate values
caused by the oscillations of the sine wave associated with ground fault currents from being displayed.
Packages CP
/
51V
: The ground fault current is a calculation of the three phase currents vectorial sum.
This measurement is suitable for line-to-ground monitoring in rigid or half-rigid earthen mains (e.g. In phase-
to-phase low voltage mains). The measured line-to-ground current should be at least 10% of the current trans-
former's rated current to ensure proper protection.
Package 50-51GN
: The ground fault current is a direct measurement of the single-phase ground current.
This measurement is suitable for line-to-ground monitoring in rigid or half-rigid earthen mains (e.g. in phase-
to-phase low voltage mains). In addition single-phase current transformers in the mains star point, in Holm-
green connection or cable-type current transformers are used for the measuring current.
Package IvIkR
: The ground fault current is a direct measurement of ground current via cable-type current
transformer.
This measurement is suitable for the line-to-ground protection in insulated or balanced mains in which very
few ground currents appear. In addition cable-type current transformers or balanced transformers in Holm-
green connection are used for the measuring current.
Displacement Voltage
Package IvIkR
: The ground fault current is a direct measurement of the displacement voltage.
The measurement is carried out via the open delta winding (e-n-winding) of a voltage transformer or via a
zero-point transformer in the generator star point.
