Quantcast Auxiliary Relays and Meters

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A hydraulic mechanism is one deriving its operating power from a fluid
accumulator in which the closing energy, prestored by compressed,
confined gas, is transmitted through the medium of a liquid (usually oil).
3.5.6.5 Auxiliary Relays and Meters. For both indoor and outdoor low-voltage and
metal-clad switchgear the relays, meters, and control switches are normally mounted on a hinged
panel attached to the circuit breaker cubicle. For outdoor oil circuit breakers the relay and meter
panel is normally mounted in a weatherproof cabinet connected to the frame of the circuit
breaker, or in some cases mounted in the mechanism housing.
3.5.7 Operation.
3.5.7.1 General Instructions. It is imperative that the operator be thoroughly familiar with
equipment tagging procedures when opening circuits. In no case shall open circuit breakers, used
for the control of lines, circuits, or station equipment, be considered as providing adequate
protection to personnel working on the associated lines, circuits, or equipment. Isolating
disconnect switches, if present, shall also be opened so there will be visible assurance that the
line or.circuit is open. If the circuit breaker is a draw-out type, the circuit breaker shall be
withdrawn and tagged before the circuit is considered cleared. Where no isolating disconnect
switches are available or the circuit breaker is not the draw-out type, the control circuits to
electrically-operated circuit breakers, which have been opened for personnel protection, must be
disconnected from the control power source. This may be accomplished by removing the fuses
or opening a switch in the control circuit, or by making the breaker inoperative by other means.
The position of the control switch handle or the indicating lamp or targets on the switchboard
should not be depended upon to determine whether the circuit breaker is open. The circuit
breaker position indicator, which is mechanically connected to the operating mechanism of the
circuit breaker, should be checked to give a more definite indication of the open or closed
position of the circuit breaker contacts.
3.5.7.2 Electrical Control. Electrically operated circuit breakers are usually controlled
from a control switch mounted on a switchboard, control desk, relay and instrument panel
associated with metal-clad switchgear, or relay and instrument panel located in a cabinet
mounted on the circuit breaker frame. All circuit breaker control switches have a hole in the
nameplate for a red and green target indicator to show the last manual operation of the switch. In
the trip position, the green signal lamp circuit can be opened by pulling the handle forward. The
handle can be latched in this position and when so latched the blackout of the lamps indicates
that the circuit controlled by the breaker is not in use. Indicating lamps are also used to indicate
the circuit breaker position. A green light indicates that the breaker is open, and a red light
indicates that the breaker is closed. On circuit breakers that are controlled from a DC power
source, the red light is commonly wired so that it is energized through the trip coil circuit of the
breaker to supervise the trip circuit and indicate that the trip coil circuit has continuity. When the
breaker is closed, a dark red lamp would indicate that the lamp is burned out or that there is an
opening in the trip coil circuit.
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