How the Doble Engineering LCM 500 is a safe measuring device ?

Why the Doble LCM 500 is a safe measuring Device for Surge Arrestor ?

The LCM 500 by Doble is an equipment used to perform checks on the surge arrester component of a power transformer.

The surge arrester’s purpose in a transformer is to protect it from possible damages due to lightning or power surge.

When lightning occurs, a high voltage is introduced into the transformer’s electrical system which is above its specified operational voltage.

This high voltage can cause damages to an electrical system that is not fitted with a surge arrester.

This is because the surge arrester, instead of absorbing the high voltage passing through it, sends it to the ground.

This is made possible by the Metal Oxide Varistor (MOV) found in the surge arrester.

The MOV works as a semiconductor which is very sensitive to the voltage going across.

At normal voltages, current do not pass through it but at high voltages, it allows current pass through it.

For its test, the LCM 500 works by measuring the state of the metal oxide varistor in the surge arrester.

Thus, the risk of failure of the surge arrester is indicated and preventives can be put in place.

It takes the LCM 500 approximately 15mins to indicate perform the test and give results of the surge arrester’s health.

Also, it shows if the transformer is still protected.

Which features Doble LCM500 provides?

The LCM 500 is a handy device, portable and battery operated thus making it easy to carry out tests without connection  to mains supply.

It has the ability to conveniently store measurement data of up to 1000 surge arrester IDs for easy management.

Its versatility is evident in that it easily differentiates individual surge types as well as their parameters of operation.

Result obtained on field can be grouped for evaluation as a being of same types as compared to others when working in regions.

What are the Doble LCM500 benefits?

The LCM 500 is a safe measuring device and effective in accurate assessment of the metal oxide in the surge arresters.

It can be used in monitoring an individual arrester so at to ascertain current changes leakages over a period of time.

It is time-saving as it doesn’t take more than 15minutes in performing a test. Also, the trest can be carried out while the arrester is operational.

Which techniques are incorporated into the Doble LCM500

The LCM 500 has a tried and tested technique of monitoring which is based on the third-order harmonic analysis and compensation.

According to the IEC 60099-5, it is rated as having the best monitoring techniques field-wise for Metal Oxide Surge Arresters (MOSA).

Measurements taken with the LCM 500 are converted automatically to conventional ambient conditions of +20oC and an arrester voltage rate times a factor of 0.7.

This is usually based on values obtained and recorded during field measurements for operating voltage and temperature.

By virtue of this, measurements gotten can therefore be compared with those taken under different field conditions.

How performing field measurements with the Doble LCM500

To perform measurements with the LCM500, the arrester’s ID is first downloaded from a PC software to the LCM500.

This is done before commencement of any inspection of surge arrester testing for its metal oxide condition.

The inbuilt memory on the handheld LCM500 device allows for storage of up to 1000 arrester IDs.

This allows for surge arrester testing of various types of surge arrester.

Hence, the correct ID of the surge arrester to be inspected can be selected at location and measurements taken.

Afterwards, measurements obtained from the field are stored and can be transferred to a PC for further analysis.

What are the LCM 500 technical specifications? 


Dimensions                             (WxHxD 47 x 35.7 x 17.6 cm
18.50 x 14.06 x 6.93 in

Weight                                     7.5 kg / 16.5 lbs


IP classification                       IP67 (closed case)
IP51 (open lid)

Operating temperature             -10°C to +50°C / 14°F to 122°F

Storage temperature                 -20°C to +70°C / -4°F to 158°F


12 – 15 VDC or 85 – 264 VAC 47 – 63 Hz

Battery                                     9.6V 2600 mAh

Capacity                                  8 hours

Charging time                          1.5 hours



Total arrester leakage current               200 – 16000 Μa

Resistive current                                  0 – 9000 μA

Frequency range                                  47 – 63 Hz (system voltage 50Hz or 60Hz)

Field probe                                          0-5Vac

Accuracy                                             ±5 % or ±5 uA


Battery powered wireless        Rechargeable (charges in instrument lid) 9V500mAh

current probe and                    Digital radio communication at 434.075 – 434.525 MHz*

field antenna                            Probes can be set at 16 distinct channels

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