Signals - ABB 615 series Technical Manual

Section 4
Protection functions
4.5.2.7
624
of a blackout. 27 is also used to initiate voltage correction measures, such as insertion of
shunt capacitor banks, to compensate for a reactive load and thereby to increase the
voltage.
27 can be used to disconnect from the network devices, such as electric motors, which are
damaged when subjected to service under low voltage conditions. 27 deals with low
voltage conditions at power system frequency. Low voltage conditions can be caused by:
• Malfunctioning of a voltage regulator or incorrect settings under manual control
(symmetrical voltage decrease)
• Overload (symmetrical voltage decrease)
• Short circuits, often as phase-to-ground faults (unsymmetrical voltage increase).
27 prevents sensitive equipment from running under conditions that could cause
overheating and thus shorten their life time expectancy. In many cases, 27 is a useful
function in circuits for local or remote automation processes in the power system.

Signals

Table 523: 27 Input signals
Name Type
V_A_AB SIGNAL
V_B_BC SIGNAL
V_C_CA SIGNAL
BLOCK BOOLEAN
Table 524: 27 Output signals
Name Type
TRIP BOOLEAN
PICKUP BOOLEAN
Default Description
0 Phase to ground voltage A or phase to phase voltage AB
0 Phase to ground voltage B or phase to phase voltage BC
0 Phase to ground voltage C or phase to phase voltage
CA
0=False Block signal for activating the blocking mode
Description
Trip
Pickup
1MAC059074-MB A
615 series ANSI
Technical Manual