Open Pilot Wires; Shorted Pilot Wires; Grounded Pilot Wires; Operating Times - GE SPA11A Instructions Manual

RELAY
Receiving End
Sending End

SHORTED PILOT WIRES

The overcurrent units in the SPA relays are normally de-energized (or dropped out).
When a short circuit of the pilot wire occurs, the current increases significantly, causing the
overcurrent unit in the sending-end relay to pick up, and causing the OC LED indicator to
light. All the current circulates through the short circuit, thereby reducing the current at
the receiving end(s) to zero. This is detected by the undercurrent unit in the receiving-end
relay(s).
A short circuit is the extreme case of the overcurrent condition. The overcurrent unit
of the sending-end relay will pick up for circulating currents of 1.35 milliamperes or
greater.

GROUNDED PILOT WIRES

When the resistance-to-ground of either conductor of the pilot wire falls below
10,000 ohms, the ground unit on the sending-end relay (normally dropped out) will pick
up and the GND indicator LED will light.
REVERSED PILOT WIRES
In the event that the conductors of the pilot wire are accidentally reversed, the
circulating current is shunted through a low-resistance path in the receiving-end relay.
This results in overcurrent detection by the sending-end relay and undercurrent detection
by the receiving-end relay. This condition is the same as in the case of shorted pilot wires.

OPERATING TIMES

The operating times of the undercurrent, overcurrent and ground detection circuits
were intentionally
made slow in order to override transient disturbances. The operating
times vary, depending upon conditions on
(e.g., two terminals versus three terminals), and the extent of the abnormal condition
the pilot wire. The values in Table V are approximate. They are intended to give a general
idea of the time involved.
GEK-65512
TABLE IV
UNDERCURRENT DETECTION LEVELS
ARRANGEMENT
2 Terminal
2 Terminal
3
Terminal
3
Terminal
the primary
7
UNDERCURRENT DETECTION
0. 53 rna or less
0.43 rna or less
0. 53 rna or less
0.21 ma or less
system, application arrangements on