Manual 37353A
MFR 13 Packages - Protection Relay
© Woodward
Page 43/91
Zero Voltage Monitoring
Function
: "Voltage within permissible limits"
All three phases of the measured voltages are below the configured limit for a zero voltage condition. This func-
tion may be used for dead bus detection and as a release signal to permit dead bus closure of the circuit breaker.
This message
cannot
be blocked with the discrete input "Blocking of protective functions / remote acknowl-
edgement". The control unit does not display a message for this condition.
Zero-voltage
Monitoring ON
Zero voltage monitoring
ON/OFF
ON
................ Zero voltage monitoring is enabled. The subsequent screens of this
function are displayed.
OFF
.............. Zero voltage monitoring is disabled. The subsequent screens of this
function are not displayed.
Zero-voltage
----------------
Monitoring type of the zero voltage monitoring
Busbar 1ph / Generator 3ph
Busbar 1ph
.. Zero voltage monitoring is performed by measuring two phases on
the busbar.
Generator 3ph
Zero voltage monitoring is performed by measuring three phases
on the generator.
Zero-voltage
V(ph-ph) <000V
Zero voltage threshold
8 to 150 V
The threshold for detecting a zero voltage condition is defined by this parameter. If
this limit is reached or fallen below, the unit does not display a message. If a relay
was assigned to this function in the relay manager, that relay will be energized.
Zero-voltage
Delay 00.00s
Pickup delay
0.02 to 99.98 s
In order to for the control to recognize a zero voltage condition, the measured volt-
age must fall below and remain below the configured threshold without interrup-
tion for at least the period of time specified in this screen.
Zero-voltage
Hysteresis 00V
Hysteresis for the zero voltage monitoring
0 to 99 V
In order to prevent system fluctuations from continually initiating a zero voltage
condition, a higher release point is defined here. If the control monitors the voltage
below the permissible limit, the voltage must rise above that threshold plus the
voltage level defined here for the fault condition to be recognized as no longer ex-
isting.
Release delay
Zerovolt. 00.00s
Release delay
0.02 to 99.98 s
To ensure that the signal relay resets after a zero voltage conditions has occurred,
the zero voltage threshold (including the hysteresis) must be exceeded without in-
terruption for the time specified by this parameter. The control will auto-
acknowledge a zero voltage condition regardless of how "Autoclearing Relays" is
configured.
NOTE
A message is not displayed on the screen for zero voltage conditions.