Woodward LS 4 Circuit Breaker Control

The LS 4 is an intelligent synchronizer and protection device capable of

measuring voltage and current though integrated measuring inputs.

It can calculate set point values using internal software routines (i.e.

for synchronization) and can transfer these set point values to a lower

level GCP control unit using the integrated CAN bus (Guidance Level). 

The LS 4 is also capable of closing the connected breaker at the

synchronous point. Additionally the measured/calculated values may

be monitored for exceeding/falling below a predefined set point result

ing in an automatic opening of the connected circuit breaker.

Electrostatic Discharge Awareness

All electronic equipment is static-sensitive, some components more than

others. To protect these components from static damage, you must take

special precautions to minimize or eliminate electrostatic discharges.

Follow these precautions when working with or near the control.

1.) Before doing maintenance on the electronic control, discharge the

static electricity on your body to ground by touching and holding a

grounded metal object (pipes, cabinets, equipment, etc.).

2.) Avoid the build-up of static electricity on your body by not wearing

clothing made of synthetic materials.

Wear cotton or cotton-blend materials as much as possible because these

do not store static electric charges as easily as synthetics.

3.) Keep plastic, vinyl, and Styrofoam materials (such as plastic or

Styrofoam cups, cigarette packages, cello phane wrappers, vinyl books or 

folders, plastic bottles, etc.) away from the control, modules, and work

area as much as possible.

4.) Opening the control cover may void the unit warranty.

Do not remove the printed circuit board (PCB) from the control cabinet

unless absolutely necessary. If you must remove the PCB from the control

cabinet, follow these precautions:

• Ensure that the device is completely voltage-free (all connectors have to

be disconnected).

• Do not touch any part of the PCB except the edges.

• Do not touch the electrical conductors, connectors, or components with

conductive devices or with bare hands.

• When replacing a PCB, keep the new PCB in the plastic antistatic protective

bag it comes in until you are ready to install it. Immediately after removing

the old PCB from the control cabinet, place it in the antistatic protective bag.

Functional Description

Introduction

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Measuring Values

• Voltage

Three-phase measurement of the rms values of the phase-to-neutral and

phase-to-phase voltages of two systems (system [A] and [B]; system [B]

only phase-to-phase). This unit can be delivered with the following measuring

voltage ranges (rated values). Selection of type during ordering: 

- 66/115 Vac - 230/400 Vac

• Frequency

Time measurement from the digitally filtered measuring voltages. The

measurement of the frequency is three phased if all voltages are greater

than 15 % of the rated value (100 Vac or 400 Vac). This guarantees a fast

and precise measurement of the frequency. However the frequency is still

measured correctly even if voltage is only applied to one phase.

• Current

Three-phase rms values.

• Real power

Single-phase measuring calculated from apparent power and power factor

cosphi (power factor).

• Re-active power

Single-phase measurement calculated from apparent power and power factor

sinphi.

• Power factor cosphi

Time measurement between the filtered measuring values of the voltage VL12

and the conductor current IL1.

General Functions

• 1 freely configurable relay output (NO) as ready for operation relay

• 4 freely configurable relay outputs (NO)

• 2 freely configurable relay outputs (change-over)

• 1 relay output (change-over) for synchronization (pulse relay)

• Discrete input for alarm blocking or acknowledgment

• Password system

• CAN bus interface

• 4 discrete control inputs

Control/Synchronization Functions

• Transmission of set point values via CAN bus to a lower level control unit

(i.e. GCP-31) for synchronization

of one circuit breaker with voltage and frequency adjustment

• Transmission of actual values via the CAN bus to a control unit (i.e. GCP-31)

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.