Directional Power, Underfrequency, And Undervoltage Protection; Arc Flash Detection; Basic Equipment Protection; Circuit Breaker Control And Control Power Protection - GE SecoGear Application Manual

SecoGear Medium-voltage Switchgear Application and Technical Guide
System and Equipment Protection
Directional Power, Underfrequency, and Undervoltage
Protection
Systems with local generation or large motors require
relaying to detect fault conditions on the utility tie circuit or
to detect loss of the utility source. Relays used to detect
these circumstances should be high-speed to trip the utility
tie prior to any automatic reclosing operations and to
promptly initiate any programmed load shedding.
Complete protection for these circumstances is provided
by a combination of functions including underfrequency
(81); a sensitive directional-power (32); and undervoltage
(27). For some applications where the (32) and (27)
functions are only instantaneous, a timer is used which is
set at about 0.2 s.
The directional-power element may be connected to
current transformers either in the incoming line circuit or in
a large motor circuit depending on the application. A study
of the specific system is required to select the appropriate
relays and connections for this type of protection.
GE Multilin multifunction relays, such as SR889 or G60, use
a combination of relay functions including underfrequency
(81), sensitive directional-power (32), undervoltage relay
(27), and timing functions to provide complete protection.

ARC FLASH DETECTION

An arc flash is the sudden release of electrical energy
through the air, following a fault. The event can produce
extreme temperatures of up to 35,000 °F, which can cause
severe damage and possible harm to employees. Due to
the nature of these events, reliable arc flash detection is
critical to avoid damage.
Two methods are commonly used: light and pressurized
sound signal detection. The GE Multilin A60 utilizes GE Light
and Pressure Sensor Technology to detect an event and
quickly send a signal to trip your breaker and remove the
energy source.
An alternate to the use of the A60 system is the GE Multilin
8 series relay along with the optional Arc Flash module
with optical sensors. The 8 Series relay and arc flash
sensors will detect light from an event and send a signal to
trip your breaker. The 8 series relay uses a combination of
32
light detection and overcurrent to reduce false indications
by some non-event light source.
Consult the GE Grid Solutions website for additional details
on the A60 and 8 Series relay systems:
www.gegridsolutions.com/products/brochures/.

BASIC EQUIPMENT PROTECTION

Circuit Breaker Control and Control Power Protection

Basic circuit breaker control consists of a control switch
located at the breaker, to close and trip the breaker.
Associated with the control switch are two indicating
lamps, one red and one green. The red lamp indicates a
closed breaker and supervises the trip coil integrity. The
green lamp indicates an open breaker. This lamp is
connected through a breaker "b" contact.
For switchgear applications requiring remote control, a
permissive control (69CS) function is available. This function
provides local or remote control of a circuit breaker under
certain defined conditions, and is available in three
schemes as shown in Table 4-1. Scheme C is
recommended for remote control, since it provides
maximum operating flexibility.
When a local "trip" operation is initiated, the breaker
cannot be closed remotely until the local switch handle is
returned to the "NORMAL AFTER CLOSE" position. When the
breaker is in the "TEST" position, closing and tripping can
only be done locally.
SecoVac VB2+ circuit breakers have a spring-operating
mechanism, consisting of a single module. The operating
mechanism is equipped with manual charging device
which uses a charging handle, and an electric charging
device which charges the spring via a motor. The
mechanism has reclose function. The front panel of the
circuit breaker shows Open/Close and Charged/Discharged
indicators and has a manual operating handle. The
operator can charge the spring remotely, manually, or by
electric power, and the status of the circuit breaker can be
observed on the front panel (Figure 2-3).
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