Woodward LS 4 Circuit Breaker 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 vol

tage 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 protec

tion 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 (us

ing 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.