Category: Basler Electric

Protection

Protection of capacitor banks has always been difficult. It is especially difficult to

sense failures inside the capacitor banks because of the configuration.

Experience indicates that most capacitor bank faults involve one or more insulator

failures with arcing across groups and/or phase-to-phase inside the bank. In most

cases, these types of faults are not seen by the bus differential or other protection

unless the arcing spills over to the area between the fuses and the circuit switcher.

A fault across an insulator usually means that one or more groups of parallel units

are shorted. This will cause a neutral shift and unbalanced phase currents.

Unbalanced phase current magnitudes are determined by the number of series

connected groups. For full phase-to-neutral flashover, the maximum phase current

is three times normal capacitor bank load in the faulted phase.

One main protection concern is overvoltage cascading. A capacitor bank is unique

in that cascading of units may take place after a predetermined number of unit

fuses have operated. Normally after a fuse has blown in any other type of equipment,

the faulted apparatus is disconnected and usually does not affect any remaining

equipment that is in service. That is not so with a capacitor bank. Each fuse that

blows to isolate the faulted unit sets up an increased voltage stress on the remaining

 units (Figure 1-1). Sometime later, the next weakest unit in that group fails.

As each successive fuse blows, the voltage increases another step and rapidly causes

the next unit to fail. Cascading takes place and results in serious damage to the

capacitor bank and possible hazards to personnel. While the capacitor bank is failing,

the station in minimally affected. The voltage is nearly normal, the current flow is almost

unaffected, and station relay protection is not taking any action until the failure has

developed into a phase-to-phase or phase-to-ground fault.

A solution was to develop a protective scheme for the capacitor bank with the main

emphasis on preventing overvoltage cascading. To do this, a ground fault relay or neutral

shift device had to be developed that was sensitive enough to detect blown fuses for both

alarming and tripping purposes. The best place to obtain the sensing information is

between the neutral of the capacitor bank and ground.

Voltage differentials between the normal capacitor bank status and that of one blown

fuse are very small.

However, BE1-59NC relays are sensitive enough to differentiate between these conditions

and act decisively.

Application

Capacitor banks are widely used by utilities to maintain specified system voltage.

Addition of capacitive loads at appropriate points on the system compensate for

heavy inductive loading that normally tends to reduce voltage.

This adding of leading megavars to compensate for the lagging megavar

component of electric loads is frequently referred to as power factor correction.

Capacitor banks must be switched in response to actual load conditions in order

to obtain maximum power factor correction benefits.

Capacitor Bank Switching

One of the common methods of maximizing capacitor bank benefits is by evaluating

the bus voltage. A bandwidth surrounding the desired bus voltage level is

established. When the bus voltage falls below the bandwidth level, the capacitor

bank is switched into the circuit. When the bus voltage rises above the bandwidth

level, the capacitor bank is switched out.

Overview

The BE1-59NC relay provides sensitive protection for capacitor banks.

Features

• Sensing circuit rejects harmonics and noise to achieve higher

sensitivity to 50/60 Hz neutral voltage.

• Includes an early warning alarm output on minor unbalances such as a

blown fuse.

• Can be set to trip when voltage across any capacitor exceeds 110% of

nominal.

Benefits

• Helps avoid cascading capacitor failures.

• Minimized PT costs as a result of low sensing burden.

• Reduced battery load with low burden power supply.

• Accurate, repeatable, and reliable operation.

• Simple HMI provides clear and intuitive settings for easy

configuration.

• LED targets provide clear annunciation of status.

• Easily perform in-case system and device tests using test plugs.

BE1-59NC Neutral Overvoltage Relays provide sensitive protection for

capacitor banks. There are three common types of capacitor bank failures

that BE1-59NC relays recognize. They are:

• Unit dielectric failure

• Capacitor bank insulator failure

• Blown fuses

BE1-59NC relays protect for overvoltage due to internal voltage shifts

that occur as a result of these types of failures.

Overview

The ruggedly designed AVC Sensing Module allows 480 Vac and 600 Vac

nominal sensing voltages to be connected to the AVC63-12 and AVC125-10

without the need for a costly step-down transformer.

Features

• Includes two inputs for 3-phase sensing voltages of 480 Vac or 600

Vac, ±10%

• Steps voltage down to 200/240 Vac for direct input to our AVC63-12 or

AVC125-10 voltage regulators.

Benefits

• Saves cost by eliminating the need for expensive sensing

transformers.

• Sensing accuracy of the AVC63-12 and AVC125-10 is preserved.

• Replaces older regulators such as the SR and SSR series when

used with the AVC63-12 or AVC125-10.

• Rugged design makes it suitable for use in extreme environments.

Overview

The BE1-50 provides high-speed detection of phase and/or ground faults.

Optional output configuration allows the relay to be used as a phase

selective fault detector.

Features

• One relay can simultaneously monitor three phases plus neutral

currents.

• Pickup setting is continuously adjustable over a wide range.

• Pickup repeatability ±2% or 40 milliamperes, whichever is greater.

• Independent output contacts for each sensing element.

• High speed operation.

• Flexible power supply provides operation from station (dc) power or line

(ac) power.

Benefits

• Easily match system configuration with single-phase, two-phase

with-neutral, three-phase, and three-phase-with-neutral input

configurations.

• Minimized CT costs as a result of low sensing burden.

• Reduced battery load with low burden power supply.

• Accurate, repeatable, and reliable operation.

• Simple HMI provides clear and intuitive settings for easy

configuration.

• LED targets provide clear annunciation of status.

• Easily perform in-case system and device tests using test plugs.

Overview

The CBS 212A provides excitation support to the generator during motor start

scenarios and faults on the generator lines. This device utilizes power current

transformers located in the generator’s output leads that provides excitation

current to the field and supplies boost to the system for motor starting and

fault clearing.

Features

• Instantaneous response to short circuits

• Up to 20 A field boost power for 10 seconds

• Activated when generator voltage drops too low to maintain field current

• For 50 or 60 Hertz brushless generators

• Covers a wide range of generator applications

• Adjustable forcing voltage limit

Benefits

• Instantaneous response by applying required excitation support,

maintaining the overall stability of the power system.

• Eliminates the need for expensive PMG and alternate systems that

provide fault-clearing or motor-starting current.

• Easy to install and configure, reducing commissioning time.

INTRODUCTION

BE3-25 sync-check relays are used to ensure that two ac

circuits are synchronized. In order to be synchronized, the

frequency, phase angle, and voltage of the two circuits must

be within preset limits. When this occurs, the BE3-25 output

relay energizes. The primary application of the BE3-25 is to

enable additional generators to be brought on-line without

machine damage or system disturbance. The BE3-25 can

also be used to supervise reclosing or in any instance where

the danger of paralleling two circuits out of synchronism

exists.

APPLICATION:

The BE3-25 series are synchronizing check relays, also known

as paralleling relays. They are used to ensure that two AC

supplies are synchronized. For a system to be synchronized,

the frequency, phase angle, and voltage must be within preset

limits. The BE3-25-****4 can monitor either utility mains bus

bar and incoming generator, or two generators. 

The BE3-25-****4 offers user adjustment of the reset voltage

from 10 to 30%. This voltage corresponds to 6 to 20 electrical

degrees. The unit compares the input voltage and phase

relationship of the bus bar to that of the generator.

When the signal is within the preset limits, the relay energizes.

The BE3-25-****5 operates as the BE3 25-****4.

but has the additional feature of a dead bus facility.

This enables the relay to energize with a generator supply

only, which is a common requirement when utility mains failure

occurs.

Benefits

• Simplify protection by covering a wide range of applications using

BE3 relays.

• Accurate, repeatable, and reliable operation.

• Most models are available for shipment from stock.

• Easy, time-saving installation with BE3 DIN-rail devices.

• Provide economical industrial protection for motor, generator,

transformer, distribution, process control, and automatic transfer

applications.

• Many BE3 relay models are self-powered, eliminating the need for

additional power sources.

BE3 Series Industrial Relays provide a wide range of cost-saving options to simplify industrial

application protection related to Auto Transfer, Distribution, Generators, Motors, Process

Control, and Transformers. Multiple DIN-rail mounting options are available.

Features

• 25 Sync-Check

• 27 Undervoltage

• 27T Undervoltage with Time Delay

• 27/59 Undervoltage/Overvoltage

• 27T/59T Undervoltage/Overvoltage with Time Delay

• 32 Reverse Power

• 37 Undercurrent

• 37/51 Undercurrent/Overcurrent

• 47 Phase Sequence

• 47N Phase Balance

• 47N/27 Phase Balance with Undervoltage

• 49R (3 or 6 RTDs) Temperature Relay

• 49TH Thermocouple Overtemperature

• 49TL Thermocouple Undertemperature

• 51 Overcurrent

• 59 Overvoltage

• 59T Overvoltage with Time Delay

• 74SL, SH, SD Millivolt Undervoltage, Overvoltage, Under/Overvoltage

• 74TL, TH, TD Milliamp Undercurrent, Overcurrent, Under/Overcurrent

• 74VL, VH, VD DC Undervoltage, Overvoltage, Under/Overvoltage

• 76SH DC Overcurrent with Inverse Time Delay

• 81O Overfrequency

• 81U Underfrequency

• 81O/U Overfrequency/Underfrequency

• 81OT Overfrequency with Time Delay

• 81UT Underfrequency with Time Delay

• 81OT/UT Overfrequency/Underfrequency with Time Delay