Metering And Test Block; Control And Transfer Switches; Surge Protection; Ansi Device Functions And Acronyms - GE SecoGear Application Manual

SecoGear Medium-voltage Switchgear Application and Technical Guide
System and Equipment Protection

Table 4-3: Multiple Ratio CTs

CT Ratio
600:5 A
50/100/150/200/250
300/400/450/500/600
1200:5 A
100/200/300/400/500
600/800/900/1000/1200
2000:5 A
300/400/500/800/1100
1200/1500/1600/2000
2000:5 A
300/400/500/800/1100/
1200/1500/1600/2000
3000:5 A
300/500/800/1000/1100/
1500/2000/2200/2500/3000
4000:5 A
500/1000/1500/2000/2500
3000/3500/4000

Metering and Test Block

Current transformer relaying accuracy and excitation
characteristics are particularly important when considering
lower-rated current transformers on systems with high
available short-circuit currents and for all differential relay
applications. Excitation characteristics and accuracy
classes are available upon request.
Standard voltage transformers are mounted in rollout
trays, with primary and secondary fusing. Models are
available rated for line-to-line, or line-to-neutral
applications with system voltages from 2400 V to 14400 V.

Control and Transfer Switches

GE Series 95 control and transfer switches are furnished, or
as specified. Test blocks and plugs can be furnished to
facilitate circuit testing, using portable instruments and
meters. The current test block is arranged so that the
current circuit is maintained when the plug is removed
from the block.
34
Standard High
Accuracy Accuracy
Class Class
C100 C200
C200 C400
C200 C400
C200 C400
C200 C400
C200 C400

Surge Protection

Every medium-voltage AC power system is subject to
transient voltages in excess of normal operating voltages.
There are many sources of transient voltages. The most
prominent ones are
• Lightning
• Physical contact with a higher voltage system
• Resonant effects in series inductive-capacitive circuits
• Repetitive restrikes (intermittent grounds)
• Switching surges
To mitigate the effects of these transient voltages, both
surge arresters and, where appropriate, surge capacitors
should be used. Surge arresters limit the crest voltage of a
voltage surge.
Surge capacitors reduce the steepness of the voltage wave
which reaches the protected equipment. Surge capacitors,
to be most effective, should be located as close to the
protected equipment (usually motors) as possible with
minimum inductance connections

ANSI DEVICE FUNCTIONS AND ACRONYMS

Table 4-4: ANSI Device Codes

Device Function
1 Master element
2 Time delay starting or closing relay
3 Checking or interlocking relay
4 Master contactor
5 Stopping
6 Starting CIRCUIT BREAKER
7 Rate of CHANGE RELAY
8 Control power disconnecting device
9 Reversing device
10 Unit sequence switch
11 Multifunction device
12 Overspeed device
13 Synchronous-speed device
14 Underspeed device
15 Speed or frequency, matching device
16 Data communications device
17 Shunting or discharge switch
18 Accelerating or decelerating device
19 Starting to running transition contractor
20 Electrically operated valve
21 Distance relay
22 Equalizer circuit breaker
23 Temperature control device
24 Volts per Hertz relay
25 Synchronizing or synchronize-check device
26 Apparatus thermal device
27 Undervoltage relay
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