Surge Arrestor Leakage Current Detector


Generally, it is said that the metal oxide surge arresters in high voltage lines should be replaced within 15 years after the start of use under the normal conditions: Of course, the duration of arresters would be shortened by various causes like as direct surge attack, internal abnormal voltage, vibration & shock to outer pole component, etc. and the regular & adequate inspections are required in order to avoid serious accidents in high voltage distribution networks.In European standard IEC60099-5 Section 6 “Diagnostic indicators of metal-oxide surge arresters”, the following inspection methods are introduced.

  • *Fault Indicators
  • *Disconnectors
  • *Surge Counters
  • *Monitoring Spark Gaps Temperature Measurements
  • *Insulation Resistance Measurements
  • *Leakage Current Measurements (Capacitive, Resistive, Harmonics, etc.)

Among various methods, the leakage current measurements (except for resistive) are only effective, as others are mostly unreliable under the very severe field conditions and some are impracticable due to impossibility of power line off for inspections

ALCL-40/ALCL-40L are adapted to “B1” method of IEC60099-5 Section 6.


The most important factor for measuring leakage current is how to detect the real & accurate values (less than 1mA) free from influences of strong magnetic & electric fields in the actual measuring places as above.
Models ALCL-40/ALCL-40L have quite unique & sophisticated CT which enables to measure very low range current with minimum resolution of 0.1μA, defending such outer electric noises.
For example, the comparison list for ordinary & ALCL CT is as followings:

RangeALCL-40/-40Ordinary Model
Minimum Resolution0.1μA10μA
Influence of Outer Magnetic FieldsLess than 10μA (400A turn/15cm)Less than 1mA (20A turn/5cm)

The operation of such field measuring instruments must be rather simple and easier.so that the inspection & maintenance can be made more frequently and the measured data compared correctly, which will lead to find out the problems of surge arresters adequately.

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Model ALCL-40/ALCL-40H/ALCL-40L


This model ALCL-40 mainly measures very small leakage current of grounding line connected with Arrester, etc. The CT which is applied to this model is hardly affected by external magnetic field and therefore, model ALCL-40 can measure leakage current very accurately in high magnetic and electric field.


1) CT Sensor

Inside Diameter of CT:37mm
Structure:Apart from Measuring Part

2) Measuring Part

Measuring Function:Leakage Current, Harmonic Current (Dominant & Third Wave)
Measuring Method:CT Clamp-on Method
Measuring Range:0-300μA/3mA/30mA (3range manual)
Input Frequency:45-60Hz (Dominant Wave Frequency)
AC Conversion:RMS Detection Method
A/D Conversion:Double Integration Method
Display:3200 count max.,LCD
Sampling Rate:2 times/second
Over Indication:”OL” on the display
Low Battery Indication:”B” sign on the display
Data Hold Function:”DH” sign on the display
Auto Power Off:Approx.10 minutes after power on
Other Function:Manually CT open/close (ALCL-40,ALCL-40H)
Motor Drive Switch for CT open/close (ALCL-40L)
Wave Form Signal Output(ALCL-40H)

3) General Specifications

Power Supply:9V Alkaline Battery (6LR61) × 1 (ALCL-40,ALCL-40H)
AA size Alkaline battery×4 (ALCL-40L)
Operating Circuit Voltage:Less than 500V AC
Operating Temperature:: 0〜40℃, less than 80%RH, w/o condensation
Storage Temperature:-10〜60℃, less than 70%RH, w/o condensation

4) Accuracy
4-1 AC Current

RangeResolutionAccuracy(45〜65Hz)Max.Applicable Current
300μA100nA(0.1μA)1.2%±8digit40A rms
AC Conversion:RMS Detection Method
Crest Factor:< 3 (0〜50% of the range)
< 2 (50〜100% of the range)

4-2 Harmonic Current(Dominant Current, 3rd Harmonic Current)

Detection Method:Automatic Tuned Filter
Min. Dominant Current Input:more than 3% of each range
Accuracy:(1%±5digit)±(AC Current Accuracy) – (Tolerance influenced by adjacent frequency)

* In case that the harmonic current is more than 4% of the dominant wave
Tolerance influenced by adjacent frequency : 1.5%

5) Dimension & Weight

ALCL-40 CT Part:135(W)×166(H)×61(D)mm, Approx. 1000g
ALCL-40H Display Part:95(W)×160(H)×334(D)mm, Approx. 260g
ALCL-40L:160(W)×950(H)×84(D)mm (when retracted rod)
160(W)×2680(H)×84(D)mm (when extended rod)
Approx. 2600g