Category: Basler Electric

Overexcitation Shutdown

Overexcitation detection provides a single-pole solid-state

contact closure across terminals A1 and A2. should the

regulator output voltage exceed 65 Vdc ±2 Vdc for a

sufficient time. For voltage above 105 Vdc ±5 Vdc, there is

a second (shorter) inverse time curve. The total inverse

time delay curve is shown in Figure 2.

After the overexcitation solid-state contact has been

made, the regulator overexcitation circuit can be reset by

decreasing the supply voltage on terminals 3 and 4 to less

than 6 Vac for a minimum of 2 seconds. This may be

accomplished by stopping the prime mover or interrupting

the regulator input by means of a reset switch. In cases

where the generator is operating in parallel mode, it may

not be desirable to allow the regulator alone to shut down

which may cause the generator to be motored. However,

continuous operation at output currents greater than the

continuous rating after the overexcitation contact has been

made may result in failure of the ac supply fuse or may

eventually cause regulator failure. If this kind of operation

will take place, an alternative external means should be

employed to protect the system.

A1 and A2 are optically isolated and floating. Any supply,

12 to 250 Vac or dc may be used, provided that current is

limited to 150 mA. Use of a dc supply to terminals A1 and

A2 will cause the solid-state device to latch after tripping.

In this case, the supply must also be removed to unlatch

the device.

FUNCTIONAL DESCRIPTION

Frequency Compensation

The frequency compensation characteristic of Figure 1 is

used to improve system load pickup performance by

restraining voltage recovery until frequency has also

started to recover. The regulator is shipped from the

factory set at a 47-Hz corner frequency for 50 Hz systems.

For 60 Hz systems, a 57-Hz corner frequency is achieved

by moving the jumper wire from the 50 and HZ terminals

to the 60 and HZ terminals.

This feature is designed to protect the generator and

regulator by allowing disconnection of the overloaded

part(s) of the system. Should the regulator be allowed to

run in excess of its rated current for any extended period

of time after the protection output closes, failure of the

recommended supply fuse will occur, but regulator

damage may also take place.

INTRODUCTION

The AEC63-7 voltage regulator is designed for use on low

voltage, 50/60 Hz brushless generators. Regulator

features include frequency compensation, overexcitation

detection and output, a solid-state buildup circuit, and

internal noise suppression.

Current Boost Logic

The Current Boost Logic, provided at terminals CB+ and

CB–, allows the regulator to enable and disable an

external Current Boost System. The interface is designed

to operate with Basler Current Boost models CBS305 and

CBS212A.

If the sensing voltage drops about 10% below the voltage

setpoint, then the Current Boost Logic will enable the

Current Boost System. Once the sensing voltage

increases to about 5% below the voltage setpoint, the

Current Boost System will be disabled.

When the Current Boost interface is not required, then no

connections should be made at terminals CB+ and CB–.

Application – Standard Models

Breaker Failure

BE1-BPR relays are intended to provide a preprogrammed solution for most

breaker failure relaying applications. Breaker failure relaying is the use of a

current monitoring relay to determine whether or not current continues to

flow into a faulted circuit after a breaker has been instructed to interrupt the

circuit. If current continues to flow into the faulted circuit after a defined

period of time has elapsed (sufficient for the breaker to have interrupted the

current), the circuit breaker is considered to have failed. Steps must then be

taken to trip the next set of breakers in the power system to prevent system

damage. Breaker failure schemes must be designed to isolate both the faulted

circuit and the failed breaker.

Several reasons why a breaker fails to clear a fault are:

• Trip circuit is open (broken wire, blown fuse, open trip coil).

• Interrupting mechanism stuck, leaving a single phase of a three-phase circuit

connected.

• Interrupter flash-over due to the loss of dielectric strength through

contamination or damage.

• Operating mechanism failed to operate.

Breaker Reclosing

BE1-BPR relays can be configured as multiple shot reclosing relays that operate in

parallel and independently from the breaker failure function.

Three major factors should be considered when establishing a reclosing philosophy.

• Desired number or reclosure attempts.

• Time delay between breaker opening and reclosure.

• Supervisory control.

The first major factor is the desired number of reclosure attempts. Where most

faults are attributable to heavy tree exposure, as in distribution networks, multiple

reclosure attempts are common. This is possible because of low voltage levels and

is desirable considering customer inconvenience during outages. BE1-BPR relays

are programmable for up to three reclosure attempts per sequence. This allows

tailoring of the reclosing sequence to the specific needs of the circuit.

The second major factor is the time delay between breaker opening and reclosure.

On sub-transmission and distribution networks, it is necessary to ensure that motors

are no longer running and that local generation is off-line prior to attempting reclosure.

At the same time, a rapid reclosure minimizes damage, ionization, and system shock

in transmission networks. After the first reclosure attempt, additional attempts are

generally delayed to allow for de-ionization of the interrupter. BE1-BPR relays have

three reclosing shots and each shot has a programmable time delay. 

Three outputs are available. They are CLOSE, RECLOSE FAIL, and LOCKOUT.

A third major factor to be considered in reclosing is supervisory control. Supervisory

control allows the operator to maintain control of the system at all times. BE1-BPR

relays have two supervisory inputs (WAIT and LOCKOUT). WAIT stops the reclose

sequence at any point and allows the sequence to continue when the WAIT input is

removed. LOCKOUT drives the reclose function immediately to lockout status and

takes precedence over all other inputs.

Breaker failure relays detect these conditions and initiate backup procedures.

Breaker failure relays are applied on a per breaker basis. That is, one breaker

failure relay for each breaker in the substation. BE1-BPR relay outputs must be

arranged to initiate the tripping of all the circuit breakers necessary to isolate

the fault if the protected circuit breaker fails to operate. The relay may also

need to initiate transfer tripping of remote breakers to accomplish this task.

Transfer tripping of the remote line end for a breaker failure should also block

reclosing of the remote circuit breakers. External lockout  relays are typically

used to trip and block reclosing of the backup breakers because they normally

require a positive operator action to reset them.

Typically, breaker failure protection is applied to transmission and sub-transmission

systems. However, breaker failure protection may be applied to any portion of the

power system where failure of a circuit breaker to operate properly could result in

severe system damage or instability. Breaker failure protection can also be used to

selectively clear a failed breaker in a station with multiple buses without clearing

the entire station.

BE1-BPR Breaker Protection Relays are three-phase and neutral, 

microprocessor based relays designed to provide power systems 

with protection and security against monitored breaker failure or

to initiate multiple shot breaker reclosings.

These relays incorporate a powerful means of programming internal

relay logic to satisfy a wide range of user requirements without making

any relay hardware changes. Microprocessor-based design provides

the basic features of a programmable logic controller (PLC) combined

with an instantaneous overcurrent module.

Cased in a 19 inch rack-mount or a vertical panel mount, the relay offers

installation versatility. A wide temperature, 2 lines by 16 character display

provides diagnostic and setup information. Two RS-232 serial ports (one

each front and rear) and one RS-485 serial port (rear) provide remote

communication and relay control.

Built-in diagnostics and monitoring features provide information for both

the health of the relay and the health of the breaker being monitored.

Relay diagnostics include continuous background monitoring of the

power supplies, analog-to-digital (A/D) converter, random-access memory

(RAM), read-only memory (ROM), and electrically-erasable programmable

ROM (EEPROM). A dedicated alarm (ALM) relay output provides power 

supply, microprocessor, and software alarm status. Breaker diagnostics

include a timing diagnostic log, breaker contact duty monitoring, breaker

resistor protection, and breaker arc detection.

Other monitoring features include oscillographic fault records and fault

summary logs. BE1-BPR relays use the Inter-Range Instrumentation Group

(IRIG), Format B for high timing accuracy and resolution.

Underfrequency Limiter

The output from one winding of the generator sensing transformer is applied to the underfrequency limiter

circuit. It is the function of this circuit to reduce the generator output voltage when the generator is operated

at less than rated speed. The percentage of generator output voltage that will be obtained for a specific

reduction in frequency is illustrated in Figures 1-1 and 1-2. The horizontal axis of the graph represents

generator frequency and the vertical axis represents the percent of nominal generated output voltage. Volts

per-hertz operation is obtained by jumping the terminals located on TS3. Limiting for 50 or 60 Hz is obtained

by proper positioning of the jumper on TS4. (Refer to Section 3. Jumper Connections)

Parallel Compensation

When two generators are operating in parallel, if the field excitation on one generator becomes excessive

and causes a circulating current flow between generators, this current will appear as a lagging power factor

(inductive) load to the generator with excessive field current and as a leading power factor (capacitive) load

to the other. The parallel compensation circuit causes the exciter-regulator to decrease the field excitation

on the generator with the lagging power factor load and increases the excitation on the other generator to

minimize the circulating currents.

Generator Sensing

Single-phase generator sensing voltage is connected at TS3-E1 and TS3-E3. Three-phase generator

sensing is connected to TS3-E1. TS3-E2. and TS3-E3. The sensing inputs are applied to the primary of

sensing transformers T3 and T4. The output voltage from the transformer(s) secondary windings is rectified

and a representative sample, taken from a voltage divider network, is applied to the automatic voltage

regulator. Selection of single-phase or three-phase sensing is done with a jumper on TS2 (Refer to Section

3. Jumper Connections).

Automatic Voltage Regulator (AVR)

The AVR senses any change in generator output voltage and translates such changes into a dc error

voltage. When the auto / manual mode switch is auto, the dc voltage is sent to the firing circuits where it

modifies the gating pulse output originally established by the manual adjust control. When the AVR

determines that the generator output voltage is low, the gating pulses are applied to the power bridge SCRs

earlier in the cycle to cause a greater dc output. When the generator output voltage is high, the gating

pulses are applied later in the cycle causing less current in the generator field.

Semiconverter Power Rectifier (Power Bridge)

The conduction time of the SCRs in the power bridge determines the amount of output current supplied to

the generator exciter field. Conduction time is controlled by the timing of gating pulses from the firing circuits.

The greater the conduction time of the SCRs, the greater the output current. The less the conduction time,

the less the output current.

Firing Circuit

The circuit compares a dc signal representative of the SCR output with a reference input established by the

manual adjust control (R5). Gating pulses to the power bridge are developed as a result of the comparison

of the two inputs. As R5 is adjusted to demand a higher or lower nominal generator output, the firing circuits

determine whether the gating pulses need to be applied earlier or later in the SCR firing cycle to establish

the new operating level. The power bridge responds by providing the correct output to the generator field.

When the auto / manual mode switch is in manual, R5 (essentially a manual voltage control) and the firing

circuits function independently of the rest of the exciter-regulator and the excitation system does not

regulate the system ac voltage. (Refer to Section 3. Controls)