Category: Basler Electric

Operating Power

Three-phase ac is applied to the power isolation transformer to provide operating power to the regulated

power supply and the semiconverter power rectifier bridge.

When the generator is placed into operation, residual voltage will pass through the normally closed contacts

of K1. It is then rectified and applied to the generator field. When the generator output voltage builds up to

a sufficient value, K1 (connected across the output of the regulator power supply) energizes, and the

contacts open, removing the voltage build-up circuits. Thereafter, the power bridge output is established by

the gating pulses from the firing circuits. The minimum residual voltage required for build-up without flashing

is approximately 5% of nominal.

Flash and Overflash Protection (SSE 250 Series Only)

This circuit provides 125 Vdc to the generator field during start-up. When the generator output voltage rises

to 35% of nominal, the flashing voltage is removed and the static exciter regulator takes over. If the output

voltage does not build up in 25 seconds, the flashing voltage removed by the overflash protection circuitry.

Introduction

The Basler Electric Shunt-Static Exciter-Regulator (SSE) controls and regulates the generator output

voltage by controlling the generator field voltage. Standard features include underfrequency or volt/hertz

operation, manual control, and provisions for paralleling. The capabilities and parameters of each model

are detailed in Table 1-1. A power input transformer is supplied as a part of the SSE.

Options

The list of options described below contains some of the options that are available on all units and may be

on your unit.

• Failed rectifier detector

• Auto / manual nulling meter

• Manual tracking motor operated potentiometer

• Over / under excitation limiting

• AC shut-down contactor

• Field flashing contactor

• Paralleling current transformers

• VAR / power factor controller

• Primary fusing for power transformer when sold in cubicle

• Metering

• Potential transformer

• Cubicles

• MOC potentiometers

• Overexcitation protective relay

• Underexcitation protective relay

Model and Style Number

Electrical characteristics and operational features included in a specific relay

are defined by a combination of letters and numbers that make up the style

number. Model number BE1-46N designates the relay as a Basler Electric

Negative Sequence Overcurrent Relay. The model number, together with

the style number, describes the options included in a specific device and

appears on the front panel, draw-out cradle, and inside the case assembly.

The positive sequence component of current (I1) represents the portion of

the total current which has normal phase rotation and produces no adverse

effect on the system. An ideally balanced system contains only positive

sequence phase currents and voltages.

The zero sequence component of current (I0) also has no adverse effect

on a three-phase, three-wire (no neutral connection) power system because

it produces no appreciable magnetic flux and causes no excessive heating

in the generator rotor or windings.

Principles of Symmetrical Components

Principles of symmetrical components allow an unbalanced system to be

considered as three separate, balanced subsystems. These balanced

subsystems may then be analyzed as single phase quantities.

These quantities are the positive, negative, and zero sequence components

of current and voltage.

The positive sequence component of current (I1) represents the portion of

the total current which has normal phase rotation and produces no adverse

effect on the system. An ideally balanced system contains only positive

sequence phase currents and voltages.

The zero sequence component of current (I0) also has no adverse effect

on a three-phase, three-wire (no neutral connection) power system because

it produces no appreciable magnetic flux and causes no excessive heating

in the generator rotor or windings.

The negative sequence component of current (I2) produces a magnetic flux

in the stator that has the same rotational speed as the rotor flux, but in the

opposite direction. This causes the stator magnetic flux to rotate at twice

the system frequency and induce eddy currents into the rotor. These eddy

currents create excessive heat in the rotor iron and windings, and, if allowed

to persist, could result in severe damage to the system.

Description

BE1-46N Negative Sequence Overcurrent Relays are three-phase solid

state relays designed to provide protection for generators and motors

from unbalanced loading or power system faults. These relays protect

the machinery from damage when the protective scheme or other

equipment, external to the generator, fails to eliminate the unbalanced

condition.

BE1-46N Negative Sequence Overcurrent Relays accurately monitor the

magnitude and control the duration of the negative sequence current

component. These relays incorporate a time delay that replicates the

machinery heating and cooling characteristics.

An alarm element in the relays may be used to provide time to locate

and isolate the fault. Doing this avoids damage to the machinery, prevents

an undesired trip, and precludes a potentially prolonged outage of the

machinery.

BE1-46N relays are designed for use with any poly-phase generating

system having known (I2)2t limits between 1 and 99. Relays that operate

using phase currents to determine the negative sequence component are

phase rotation sensitive. BE1-46N relays are phase rotation sensitive.

PUSH-TO-ENERGIZE OUTPUTS

A push-to-energize pushbutton is included for each tripping output contact. These pushbuttons can be

used to verify correct operation of external control circuit wiring without the need to supply test signals to

the relay. Control power must be applied for this function to operate. The pushbuttons are recessed

behind the relay front panel and are not accessible with the cover installed.

TARGETS

One target is included for each tripping function as specified by style number. Targets are operated either

by the internal signal initiating tripping (internally operated) or by a minimum of 200 mAdc flowing through

the series circuit consisting of the target coil and output relay contacts (current operated). Within a

specific relay, all targets must be operated in the same way.

POWER SUPPLY OPTIONS

Various power supply options are available to allow the BE1-67N relay to be used with standard supply

voltages. See the style chart for details.

POWER-UP DELAY

A power-up delay timer is initiated upon application of control power to the relay to prevent undesired

contact transitions when sensing signals are present. Operation of measuring circuits and output circuits

are inhibited (less than 0.5 seconds) until the power-up delay period has expired.

Zero Sequence Current

Zero sequence current polarization is preferred for applications with low ground source impedance.

Figure 1-1 illustrates relay connections that obtain zero sequence current (3I0

) from a separate current

transformer in the grounded neutral of a two winding wye-delta power transformer. Figure 1-2 illustrates

relay connections that obtain zero sequence current from a current transformer(s) in the grounded

neutral(s) of a three winding transformer. The magnitude of the zero sequence current used for polarizing

may be different from that of the ground current seen by the measuring element(s) of the relay.

Zero Sequence Voltage

Zero sequence voltage polarization is preferred for higher ground source impedances. Refer to Figures 1

1 and 1-2 for relay connections that obtain zero sequence voltage (3V0

) from a set of grounded wye

broken delta voltage transformers. The voltage polarized relay has a directional polarization adjustment to

match the impedance angle of the protected line to the characteristic angle of the relay. This is the angle

about which the directional angle is centered. A choice of line angles allows the relay to be adjusted to

include the resistance component of the ground fault.

RESTRAINT CHARACTERISTICS

At high current levels, the inevitable difference in the

saturation characteristics between current transform

ers requires a compensating decrease in relay

sensitivity. The design of the BE1-87G provides a

restraint factor that is proportional to input current.

Specifically, the BE1-87G compares the two sensed

currents (in and out) to determine which is less. This

lower current level becomes the restraining current.

The difference between the two sensed currents (I0

) is compared to a reference established by the sensitivity

setting and adjusted by an amount proportional to the

restraining current. (The typical ratio is given in the

formula on page 3.) This makes the BE1-87G more

sensitive to low current internal faults, for which the

relay should operate, and less sensitive to external

faults with high levels of through current for which the

relay should not operate.

Dual Zero Sequence Current and Voltage

Dual polarization is preferred where ground source impedance varies, or to provide redundant

polarization. Dual polarization is achieved using a polarizing signal that is the phasor sum of the current

and voltage polarizing signals.

OUTPUT CONTACTS

BE1-67N relays have the following output contacts: relay status alarm (relay fail), tripping, and auxiliary

(optional).

Relay Status Alarm

A relay status alarm output contact (relay fail) indicates that proper voltages are not being supplied to the

internal relay circuitry or that the microprocessor self-diagnostics has detected an error. This alarm output

contact is normally closed.

Tripping

Normally open or normally closed tripping contacts are included for each function within the relay.

Configuration of these contacts is defined by the relay style number. These output contacts are used with

optionally selected target indicator circuits.

Auxiliary

Normally open, normally closed, or single pole double throw (SPDT) auxiliary contact configurations are

provided to act in parallel with the tripping function(s) of the relay. Configuration of the auxiliary output

contacts are also defined by the relay style chart.

An auxiliary contact can be configured (via internal switches) to operate in parallel with any combination

of tripping outputs. Configurable auxiliary outputs permit use of the BE1-67N relay in various carrier

schemes.

PURPOSE

BE1-67N Ground Directional Overcurrent Relays provide ground fault protection for transmission and

distribution lines by sensing the flow of ground (zero sequence) current into or out of protected zones.

Zero sequence quantities provide a secure reference for the directional element because these quantities

are defined by the total source impedance of the power system.

APPLICATION

BE1-67N Ground Directional Overcurrent Relays are recommended for multi-grounded systems to

provide coordination necessary to selectively trip the faulted line. A directional overcurrent relay operates

by comparing the measured current to a reference quantity to determine whether current is flowing into or

out of the protected zone. Reference quantity is also referred to as polarizing quantity.

BE1-67N relays use one of the following quantities for polarization:

• Zero sequence current

• Zero sequence voltage

• Dual zero sequence current and voltage

The polarizing quantity is field selectable using a switch mounted on the analog circuit board. When the

selected polarizing quantities are less than the minimum threshold, relay operation will be inhibited. When

using dual polarization, the relay will operate if either polarizing quantity is above minimum threshold.