Siemens ISGS SG8158-00 - Manual (Page 112)

Glossary
G-iv Siemens Energy & Automation, Inc.
trip to occur. If the underfrequency condition subsides in less
time than the delay time, the pickup will go inactive and the
underfrequency function will reset. When tripping occurs, the
actual condition that caused the trip is recorded in the
device's nonvolatile trip log. Pickup occurs when the fre-
quency in greater than the pickup setting.
Undervoltage (27) Relay function that protects against a
line-to-line undervoltage condition. Tripping occurs when the
rms value of any one line-to-line voltage drops below the
programmed undervoltage pickup for a period of time equal
to the delay time setting. The pickup must remain active for
the entire delay time for a trip to occur. If the undervoltage
condition subsides in less time than the delay time, the
pickup will go inactive and the undervoltage function will
reset. When tripping occurs, the actual condition that caused
the trip is recorded in the device's nonvolatile trip log. Pickup
occurs when any one line-to-line voltage is less than the
pickup setting.
value supervision The ability of the ISGS relay to monitor
its own input and measurement functions for problems.
Voltage Balance Relay function that protects against an
unbalance in the phase voltages. The function monitors the
phase voltages for approximate balance (of equal magni-
tude). Balance is defined as the ratio of minimum to maxi-
mum voltage, where the maximum voltage is the largest and
the minimum voltage the smallest of the three phase volt-
ages. The voltage is considered balanced and will not cause
an alarm if the voltage min/max ratio is larger than the volt-
age balance factor. The voltage balance factor indicates the
amount of unbalance tolerated before the function generates
an alarm. The function monitors for balance when the maxi-
mum voltage is larger than the voltage balance pickup value.
An alarm occurs when the min/max ration is smaller than the
voltage balance factor.
VT Configuration A function to set up an ISGS relay with
voltage input option to match VT primary rating and VT con-
nection settings of an electrical distribution system.
Warning Indicates a potentially hazardous situation which,
if not avoided, could result in death or serious injury.
G
isv3o_1.bk : isv30_gl.frm Page iv Wednesday, August 7, 1996 10:51 AM