Woodward LS 4 Circuit Breaker Control

for real power control

• Closing of the CB onto a dead (de-energized) bus bar

Power Factor Definition

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The phasor diagram is used from the generator's view. This defines the following

definitions.

Power Factor is defined as a ratio of the real power to apparent power. In a purely

resistive circuit, the voltage and current waveforms are instep resulting in a ratio

or power factor of 1.00 (often referred to as unity). In an in ductive circuit the

current lags behind the voltage waveform resulting in usable power (real power)

and unusable power (reactive power). This results in a positive ratio or lagging

power factor (i.e. 0.85lagging). In a capacitive circuit the current waveform leads

the voltage waveform resulting in usable power (real power) and unusable power

(reactive power). This results in a negative ratio or a leading power factor (i.e.

0.85leading).

Function

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Synchronizing

The variable system is synchronized to the fixed system (variable and fixed system

can be configured) for voltage and frequency. This is done by sending set point

values through the CAN bus to the lower level GCP control that are electrically

connected with the configured variable system. The LS 4 calculates the correct

synchronous point to issue a CB close command using the switching time of the

CB (Parameter 37). Synchronizing/closing of the CB is done if the following

conditions are fulfilled simultaneously:

• The unit is in automatic mode.

• The synchronizing function is enabled (Parameter 31).

• Voltage and frequency of both systems [A] and [B] are within the configured

range (for both systems this range is adjustable by changing the settings for the

voltage monitoring functions of system [A] if this protection is enabled;

Dead Bus Start

A close CB command without synchronization may be issued if the following

conditions are fulfilled simulta neously:

• Dead bus start function is configured to ON (Parameter 43).

• Discrete input "Enable CB" is set.

• Discrete input "Reply: CB is open" is set.

• One of the three possible black start functions is enabled

1.) Parameter 46 (Vsystem A=Vn/Vsystem B=0)

Vsystem A is equal with Vn (using the configured rated voltage difference dV

|V-Vn|) and Vsystem B is zero (using the configured zero voltage difference

dV |V-0|).

2.) Parameter 45 (Vsystem A=0/Vsystem B=Vn)

Vsystem A is zero (using the configured zero voltage difference Vd |V-0|) and

Vsystem B is equal with Vn (us

ing the configured rated voltage difference dV |V-Vn|).

3.) Parameter 44 (Vsystem A=0/Vsystem B=0)

VA is zero and VB is zero (using the configured zero voltage difference dV |V-0|).

• No alarm is triggered if parameter "Blocking at dead start alarm" is configured

to ON (Parameter 51).

• No GCP is trying to carry out a dead bus start.

• No higher prioritized LS 4 is trying to close its breaker.