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 synchroni

zation) 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. Addition

ally 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 sys

tems (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 (see page 75 "Technical Data"): 

- 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 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.