Category: Basler Electric

APPLICATION

In general, power transformers have different values of current flowing through their primary, secondary,

and tertiary windings. These currents have specific phase relationships depending upon the connections

of the individual windings (e.g., wye/delta). As inputs to a differential relay, these currents must be

compensated or scaled so that the relay can compare the inputs and determine when an unbalance

exists. Under ideal operating conditions, the scaled vector sum of these currents is zero.

Because it is practically impossible to match the magnitudes of these detected currents from the various

power windings using standard CT ratios, the currents are matched within the relay by scaling each of the

applied currents by an appropriate factor called a Tap Setting. This is set by means of the front panel

INPUT dials. By selecting suitable tap ratios, the applied currents are scaled within the relay to achieve

the desired balance for normal operating conditions. BE1-87T relays offer a range of available tap settings

for inputs between 0.4 A to 1.78 A (Sensing Input Range Options 2 and 4 for a 1 A CT) or 2.0 to 8.9 A

(Sensing Input Range Options 1 and 3 for a 5 A CT). These settings are independently adjustable in

increments of 0.02 A for Sensing Input Range Options 2 and 4. or 0.1 A for Sensing Input Range Options

1 and 3. These small increments allow more precise scaling of the applied currents and usually eliminate

the need for installing auxiliary ratio-matching CTs.

DESCRIPTION

BE1-87T Transformer Differential Relays provide primary protection for power transformers and are

available in either Single-Phase or Three-Phase configurations. The solid-state BE1-87T compares the

currents entering and leaving the protected transformer. If a fault is detected, the relay initiates a trip

signal to isolate the power transformer. This limits damage to the transformer and minimizes the impact

on the power system.

BE1-87T relays use three types of restraint:

• Percentage of through-current

• Second harmonic

• Fifth harmonic

Selectivity in differential relaying is based on the ability to distinguish between internal and external faults.

This is achieved by comparing the currents into and out of a power transformer. Comparing these

currents often requires more than two inputs. For example:

• Power transformers may have a significant portion (greater than 10 %) of the current flowing in a

third or tertiary winding.

• Power transformers can have multiple breakers for a given winding (e.g., ring bus or breaker

and-a-half bus).

BE1-87T relays are available with up to five restraint inputs for the single-phase unit and up to three

restraint inputs per phase for the three-phase unit.

Compatibility with accessories such as excitation limiters, power factor

controllers, auto synchronizers, and excitation support systems makes

it an ideal modernization  solution for existing generator systems.

Its rugged construction, direct-replacement design, and proven

performance help extend equipment life while improving regulation

accuracy and reliability.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

Operation

The FGD-2 continuously monitors the machine field circuit for ground faults.

Ground faults are detected through the measurement of leakage current to

ground which is determined by measuring the voltage drop across a shunt

resistor within the ground detector source. The Basler device connected to

the FGD-2 receives a voltage signal from the ground detection source that

is proportional to the level of field leakage current. The excitation

capabilities and analog input ranges of different Basler products will limit

the maximum compatible field voltage for accurate field ground resistance

measurements. Refer to Table 2 for more details.

AIOM-2

In a DECS-2100 system, the AIOM-2/AIOM digitizes the signal and transmits

it via fiber optic cables to the ECM-2. In an ECS2100 system, the digitized

signal is received by the ECM/SIM. The value of leakage current appears as

an input to the BESTCOMS™Pro FLDGND logic block. Within the FLDGND

logic block, a value of resistance to ground is calculated from the voltage

applied and the level of leakage current measured. Typically, this calculated

resistance value is transmitted to a display panel via the PMOUT logic block.

In the event of a low field ground resistance value, the FLDGND logic block

issues a Low Field Ground Resistance alarm. During detection of low field

ground resistance, an alarm issued by the DIGROUT logic block can be used

to energize a relay within the system’s Digital I/O Module (DIOM-2 or DIOM).

This annunciation may be used to provide a dry relay contact for a remote

alarm.

The SR4A Retrofit Voltage Regulator is an economical, direct replacement

for existing Basler Electric SR4A voltage regulators. Designed for brush

and brushless synchronous generators, it delivers accurate voltage

regulation, dependable excitation control, and fast response times while

fitting within the same mounting footprint as the original regulator. 

The retrofit package incorporates a modern AVC63-12 voltage regulator

and, where required, an internal sensing module, making installation

quick and straightforward.

Engineered for reliable operation in demanding power generation

environments, the SR4A Retrofit supports single- or three-phase sensing,

reactive droop compensation, line drop compensation, underfrequency

protection, and integration with power factor controllers, excitation limiters,

and auto synchronizers. Its rugged construction, ease of installation, and

compatibility with existing generator systems make it an ideal solution for

extending equipment life and improving voltage regulation performance.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

The SR9A Retrofit Voltage Regulator is an economical, direct replacement

for existing Basler Electric SR9A voltage regulators.

Designed for synchronous generators operating in 400 Hz applications,

it provides accurate voltage regulation, fast response times, and dependable

excitation control while utilizing the same mounting footprint as the original

regulator. The retrofit solution incorporates a modern AVC125-10 voltage

regulator and, where required, an internal sensing module to streamline

installation and reduce maintenance requirements.

Built for demanding power generation environments, the SR9A Retrofit

supports single- or three-phase sensing, reactive droop compensation,

line drop compensation, underfrequency protection, and integration with

accessories such as power factor controllers, excitation limiters, and auto

synchronizers. Its rugged construction, reliable performance, and

straightforward upgrade path make it an ideal solution for extending the

life and functionality of existing generator systems.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

The SR8A Retrofit Voltage Regulator is an economical, direct replacement

for existing Basler Electric SR8A voltage regulators. Designed for brush

and brushless synchronous generators, it delivers precise voltage regulation,

fast response times, and dependable excitation control while fitting within

the same mounting footprint as the original SR regulator.

The retrofit package incorporates a modern AVC125-10 voltage regulator and,

where required, an internal sensing module, simplifying installation and

minimizing downtime.

Engineered for reliability in demanding power generation applications, the

SR8A Retrofit supports single- or three-phase sensing, voltage matching,

reactive droop compensation, line drop compensation, and underfrequency

protection. Its rugged design withstands harsh industrial environments,

while compatibility with accessories such as excitation limiters, power factor

controllers, and auto synchronizers makes it a versatile solution for generator

upgrades and modernization projects.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

The SR6A Retrofit Voltage Regulator is an economical, direct replacement

for existing Basler Electric SR6A voltage regulators used in 400 Hz

generator applications. Designed to fit within the same mounting footprint

as the original regulator, it provides accurate voltage regulation, fast

response times, and dependable excitation control for brush and brushless

synchronous generators. The retrofit package incorporates a modern AVC63

-12 voltage regulator and, when required, an internal sensing module, making

upgrades straightforward and cost-effective.

Built for reliable performance in demanding power generation environments,

the SR6A Retrofit supports single- or three-phase sensing, reactive droop

compensation, line drop compensation, underfrequency protection, and

accessory integration. Its rugged construction, compatibility with existing

systems, and easy installation make it an ideal solution for extending the

service life of legacy generator voltage regulation systems while improving 

performance and maintainability.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

The SSR63-12 Retrofit Voltage Regulator is an economical, direct

replacement for existing Basler Electric SSR63-12 voltage regulators

used with brushless synchronous generators. Designed to fit within

the same mounting footprint as the original regulator, the retrofit

solution incorporates a modern AVC63-12 voltage regulator and,

when required, an internal sensing module.

It delivers precise voltage regulation, dependable excitation control,

and fast response times while minimizing installation time and upgrade

costs. Engineered for demanding generator applications, the SSR63-12

Retrofit supports single- or three-phase sensing, reactive droop

compensation, cross-current compensation, line drop compensation,

and underfrequency protection.

Compatibility with accessories such as excitation limiters, power factor

controllers, auto synchronizers, and excitation support systems makes

it an ideal modernization  solution for existing generator systems.

Its rugged construction, direct-replacement design, and proven

performance help extend equipment life while improving regulation

accuracy and reliability.

The SR and SSR Retrofit Voltage Regulators are designed as economical,

direct replacement solutions for legacy Basler SR and SSR voltage regulators.

Engineered for quick installation, these retrofit kits fit into the existing

mounting space and utilize terminal-to-terminal wiring to simplify field

replacement. Integrated CT input burden matching supports paralleling

systems with cross-current compensation, while accessory inputs provide

compatibility with var/power factor controllers and excitation limiters.

The SR and SSR Retrofit series delivers the same dependable performance

as the original regulators while helping extend the life and reliability of

generator excitation systems.

— Product Features & Benefits

• Installation into the same space previously occupied by a Basler Electric SR

or SSR regulator without additional mounting holes and/or hardware.

• Terminal-to-terminal wiring allows quick field replacement of the original

voltage regulator.

• Integrated CT input burden matching provides compatibility with paralleling

systems utilizing cross-current compensation.

• An accessory input provides compatibility with devices such as var/power

factor controllers or excitation limiters.

• Same reliable operation as the original SR/SSR being replaced.

• Standard retrofit kits easily replace multiple models, including custom models,

of the Basler SR and SSR voltage regulators.