efrem data sheet rev 7

7/26/2019 EFREM Data Sheet Rev 7

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Applications:

Rotor Protection throughCondition BasedMaintenance

Predictive Maintenance -for large generators andmotors

Benefits:

Continuous On-linemonitoring of faults - whilerotating or at standstill

Trending - of fault severityresistance

Indication of faultlocation

Field excitation voltage -also continuously monitored

Alarm relay contactoutputs- for multipleresistance limits.

Rotor Field Ground Detector:

(EFREM)Earth Fault Resistance MonitorThe Earth Fault Resistance Monitor (EFREM) provides

continuous wireless monitoring of insulation fault resistance

and field voltage on brushless exciter generator/ motor field

windings, combining advanced ground fault measurement

techniques with the latest innovations in digital telemetry.

Introduction

Building on a decade long track record of innovation ingenerator / motor rotor protection, with an installed base of

hundreds of machines, Accumetrics is proud to introduceEFREM-- its latest generation of rotor field ground faultdetection technology.

The Earth Fault Resistance Monitor (EFREM) provides: Quantitative values of fault severity (continuous resistance

measurements) trend your high accuracy data readings! Continuous monitoring for faults (always operational, while

rotating and when off line) Fault location indicator for ease of diagnosis and repair Field excitation voltage level monitoring Alarm relay contact outputs for multiple resistance limits (for

instance, an early warning alarm and a machine trip).

Earth Fault Resistance Measurement Technology

The detection of field ground faults on generators orsynchronous motors with brushless exciters has always beendifficult. Conventional field ground detectors may detect theoccurrence of faults but provide no advance warning orindication of the faults severity. In fact, the severity at thedetection threshold may vary by several orders of magnitude,depending on fault location. Now, by combining its latest 16 bitdigital rotor telemetry technology with the most sophisticated

technique available for generator ground fault measurements,Accumetrics overcomes these limitations with EFREM.Measurement of actual resistance allows users to monitor trendsover time and track the progression of ground faults from theironset. This provides an early warning of impending failure andallows for predictive maintenance of a machine. The severity ofground faults can be used in making operational andmaintenance decisions.

Continuous On-Line Monitoring--

Resistance Trending for Ground Fault

Generator/Motor Rotor Protection


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Accumetrics quantitative measurement overcomes the uncertainties of conventional ground faultdetectors by measuring actual ground fault resistance and field voltage. In addition, the techniqueyields a location factor, which indicates where the fault occurs along the length of the field winding.

Specifications:Rotor Connections Field Positive Terminal

Field Negative TerminalRotor Earth

Measurement Range 0 to 500 VDC. (Contact factory for other ranges)Field VoltageMaximum Transient withoutdamage

1000 Volts for 5 seconds

Measurement Range 0 to 80 MResistance Measurement

Accuracy 2500.5% of Reading 0 to 500 K( exclusive of the effectsof AC content and noise from the excitation system)

Range 0 to 100% representing ratio of potential at fault to total fieldvoltage (0 at negative terminal and 100% at positive terminal)

Earth Fault Location Factor

Accuracy 1% for a 10Kfault and Field Excitation 25VEarth Fault Two independent alarm resistances, user selectable via computer

interface from 500to 1MMalfunction Active upon detection of a malfunction in Monitor operation or loss

of receiver power.

Receiver Alarm Outputs

Alarm interfaces Form C relay: 10A/24VDC, 0.3A/240VDC, 10A/250VAC resistiveReceiver Analog Outputs Analog outputs Dual analog output of Field V and Log Resistance (4/20mA)

Computer interfaces RS232, EthernetOutput Data Earth Fault Resistance, Field Voltage, Location Factor when faults

occur, Alarm and error conditions

Receiver Digital Interface

User Settings Earth Fault Alarm Resistance Thresholds, Alarm Dwell Time,Network Settings

Ambient Temperature 0 to 85C at Rotor Module

0 to 50C at Receiver Unit

Environment

Rotor Speed 0 to 3600 RPMReceiver Power 85 to 250VAC 50/60Hz,


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End-of-Shaft (Center-line)

Mounted

Mid-Shaft Mounted


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Typical System Configuration

(End-of-shaft mounting version)

Transmitter:

--Rotating assembly

(end-of-shaft

mounting), with

connections for rotor

ground, and positive/

negative field

terminals

Pickup Antenna:

--Stationary induction

power/ data, with coaxial

cable connection to

Receiver

Receiver:

--3 alarm relays, Ethernet

and RS232 outputs, with

4/20mA (or voltage) outputs

of field voltage and log

insulation resistance

RS232, Ethernet Output:

--Software for charting/

trending display of fault

resistance and display of roto

field voltage.

--PC Archive software (for

Excel data storage) optional

efrem data sheet rev 7

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