Category: ABB

Event log

To collect sequence-of-events information, the relay has a

nonvolatile memory capable of storing 1024 events with the

associated time stamps. The event log facilitates detailed pre

and post-fault analyses of feeder faults and disturbances. The

considerable capacity to process and store data and events in

the relay supports the growing information demand of future

network configurations.

The sequence-of-events information can be accessed either via

the LHMI or remotely via the communication interface of the

relay. The information can also be accessed locally or remotely

using the Web HMI.

Self-supervision

The relay’s built-in self-supervision system continuously

monitors the state of the relay hardware and the operation of

the relay software. Any fault or malfunction detected is used for

alerting the operator.

A permanent relay fault blocks the protection functions to

prevent incorrect operation.

Load profile

The load profile recorder stores the historical load data

captured periodically (demand interval). Up to 12 load

quantities can be selected for recording and storing in the

nonvolatile memory. The recordable quantities include

currents, voltages, power and power factor values. The

recording time depends on a settable demand interval

parameter and the amount of quantities selected. The

quantities’ type and amount to be recorded are determined in

the application configuration. The recorded quantities are

stored in the COMTRADE format.

The relay’s built-in self-supervision system continuously

monitors the state of the relay hardware and the operation of

the relay software. Any fault or malfunction detected is used for

alerting the operator.

A permanent relay fault blocks the protection functions to

prevent incorrect operation.

Recorded data

The relay can store the records of the latest 128 fault events.

The records can be used to analyze the power system events.

Each record includes, for example, current, voltage and angle

values and a time stamp. The fault recording can be triggered

by the start or the trip signal of a protection block, or by both.

The available measurement modes include DFT, RMS and

peak-to-peak. Fault records store relay measurement values

when any protection function starts. In addition, the maximum

demand current with time stamp is separately recorded. The

records are stored in the nonvolatile memory.

The trip circuit supervision continuously monitors the availability

and operability of the trip circuit. It provides open-circuit

monitoring both when the circuit breaker is in closed and in

open position. It also detects loss of circuit-breaker control voltage.

Self-supervision

The relay’s built-in self-supervision system continuously

monitors the state of the relay hardware and the operation of

the relay software. Any fault or malfunction detected is used for

alerting the operator.

A permanent relay fault blocks the protection functions to

prevent incorrect operation.

Trip circuit supervision

The trip circuit supervision continuously monitors the availability

and operability of the trip circuit. It provides open-circuit

monitoring both when the circuit breaker is in closed and in

open position. It also detects loss of circuit-breaker control voltage.

The recordable quantities include

currents, voltages, power and power factor values. The

recording time depends on a settable demand interval

parameter and the amount of quantities selected. The

quantities’ type and amount to be recorded are determined in

the application configuration. The recorded quantities are

stored in the COMTRADE format.

Disturbance recorder

The relay is provided with a disturbance recorder featuring up to

24 analog and 64 binary signal channels. The analog channels

can be set to record either the waveform or the trend of the

currents and voltages measured.

The analog channels can be set to trigger the recording function

when the measured value falls below or exceeds the set values.

The binary signal channels can be set to start a recording either

on the rising or the falling edge of the binary signal or on both.

The binary channels can be set to record external or internal

relay signals, for example, the start or trip signals of the relay

stages, or external blocking or control signals. The recorded

information is stored in a nonvolatile memory in COMTRADE

format and can be uploaded for subsequent fault analysis.

The protection relay has the following power quality monitoring

functions.

• Voltage variation

• Voltage unbalance

• Current harmonics

• Voltage harmonics

The voltage unbalance and voltage variation functions are used

for measuring short-duration voltage variations and monitoring

voltage unbalance conditions in power transmission and

distribution networks.

The voltage and current harmonics functions provide a method

for monitoring the power quality by means of the current

waveform distortion and voltage waveform distortion. The

functions provide selectable short-term 3- or 60- or 300

second sliding average and a long-term demand for total

demand distortion (TDD) and total harmonic distortion (THD).

The phase-specific harmonic content is measured for voltages

and currents, as well as DC component and fundamental

content. The dedicated harmonics measurement page in the

LHMI presents the measurements in a user-friendly manner.

Power quality

In the EN standards, power quality is defined through the

characteristics of the supply voltage. Transients, short-duration

and long-duration voltage variations and unbalance and

waveform distortions are the key characteristics describing

power quality. The distortion monitoring functions are used for

monitoring the current total demand distortion and the voltage

total harmonic distortion.

Power quality monitoring is an essential service that utilities can

provide for their industrial and key customers. A monitoring

system can provide information about system disturbances and

their possible causes. It can also detect problem conditions

throughout the system before they cause customer complaints,

equipment malfunctions and even equipment damage or

failure. Power quality problems are not limited to the utility side

of the system. In fact, the majority of power quality problems

are localized within customer facilities. Thus, power quality

monitoring is not only an effective customer service strategy but

also a way to protect a utility’s reputation for quality power and

service.

Measurements

The base functionality of the REX640 relay contains a number of

basic measurement functions for current, voltage, frequency,

symmetrical components of currents and voltages, power,

power factor and energy. These measurement functions can be

freely connected to the measured secondary quantities

available in the relay. The relay can also measure various analog

signals via RTD and mA inputs. All these measurements can be

used within the relay configuration for additional logics. The

measurements are available locally on the HMI and can be

accessed remotely via communication. The information is also

accessible via Web HMI.

The relay is also provided with a load profile recorder. The load

profile feature stores the selected load measurement data

captured periodically (demand interval). The records can be

viewed on the LHMI and are available in COMTRADE format.

Power transformer differential protection

The relay offers low-impedance differential protection for two

winding (two restraints) and three-winding (three restraints)

power transformers. The power transformer protection

application package includes the protection for a two-winding

power transformer. If support for three-winding power

transformer is needed, the corresponding protection add-on

package can be selected. Both low-impedance differential

functions feature three-phase multi-slope stabilized stages and

an instantaneous stage to provide fast and selective protection

against short circuits, winding interturn faults and bushing

flash-overs. A second harmonic restraint with advanced

waveform-based blocking ensures stability at transformer

energization. The fifth harmonic based blocking and unblocking

limits stabilize the protection performance in moderate

overexcitation situations. In case of three-winding differential

protection, the connection group phase shift matching can be

done with 0.1 degree resolution supporting cycloconverter

applications. If the tap-changer position information is

available, it is possible to further increase the protection

sensitivity by compensating the tap-changer position error

within the measured differential current.

Arc flash protection

The arc flash protection is available on the optional hardware

module. The module supports connection of up to four sensors.

The sensors can be of lens or loop types, or a free mixture. Both

sensor types are supervised against sensor failure. Fast tripping

increases staff safety and limits material damage, therefore it is

recommended to use static power outputs (SPO) instead of

normal power outputs (PO). This typically decreases the total

operating time with 4..6 ms compared to the normal power

outputs.

The power transformer protection application package also

includes high-impedance differential functions for a phase

segregated protection scheme. If this scheme is applied, the

related current transformers have to be correctly selected and

the necessary secondary circuit components, external to the

relay, defined.