Transformers are critical components of modern transmission and distribution networks, even if they themselves can be antiquated. With transformer investment peaking in the 1960s and 70s we are now seeing large numbers of transformers operating beyond their intended lifespans. To compensate for a lack of investment the condition monitoring of this aged stock is even more paramount. Continuous online fault gas analysis allows for early detection of critical situations and prompt transformer fault detection enabling timely preventative maintenance to be initiated. This leads to:

Less risk of unplanned power outages
Less maintenance work on site
Enhanced service reliability and better operational efficiency
A reduction in the risk of catastrophic failures
Extension of the transformer lifetime
A more secure high voltage power transmission system
Customised and tailored monitoring of strategically important power transformers
Optimisation of insurance costs

Drallim Industries Limited is the sole UK & Ireland representatives of the Meter Test Equipment (MTE) range of transformer monitoring systems. Since 1996 the name MTE has been synonymous with innovation, functionality, accuracy and quality in manufacturing test equipment and monitoring systems. As one of MTE’s carefully chosen distributor companies we can use our expert industry knowledge and the skills of first-class hardware and software engineers to find solutions for our customers.

The Hydrocal Range

There are five main HYDROCAL units available for dissolved gas analysis of individual transformers. Each can be directly mounted with ease onto an operating transformer via a boss with a 1 ½” NPT or DIN ISO thread without any operational disruption (flange adaptors are available). These units accurately measure the moisture in oil (H2O) content because it is a well-known fact that an upward trend of moisture content in transformer oil is a key indication of an incipient fault.

Composite Fault Gas Analysis

A composite sensor uses a weighted Total Dissolved Combustible Gases (TDCG) algorithm that gives an inference of transformer health. An upward trend of any key fault gas is an indication of the presence of an incipient fault. Finding this fault early allows preventative action to be taken in a timely manner before any faults can become critical.
For more information on the Hydrocal 1001+ composite fault gas sensor please use the data sheet link below.

The HYDROCAL 1001+

A permanently installed composite gas-in-oil sensor for the analysis of the six key fault gases: Hydrogen (H2), Carbon Monoxide (CO), Methane (CH4), Acetyne (C2H2), Ethylene (C2H4) and Ethane (C2H6) and moisture H2O.

Individual Fault Gas Analysis

For specific transformer oil, dissolved gas analysis MTE have engineered four Hydrocal monitors that analyse for specific individual fault gases. The ability to monitor individual gases reduces the amount of maintenance time because likely causes of any incipient faults will have been established before pre-emptive action takes place. These four online DGA units come complete with a large backlit graphical LCD display for local monitoring. Each unit also includes 4-20mA Analogue outputs that can individually transmit data concerning the analysed moisture in oil and applicable key fault gases for remote monitoring. Integrated MODBUS communication capability over ETHERNET and RS-485 are included and optional communication configurations are also available. Hydrosoft PC Software is supplied for remote monitoring that enables configuration and administration of each individual HYDROCAL unit. This software allows data trends to be easily processed and be presented in tables and graphs. This data can also be exported to Microsoft Excel and Clipboard allowing further processing and presentation capabilities.

For more detailed information on these Hydrocal monitoring systems please use the links to the data sheets below.

The HYDROCAL 1003 (offshore version available)

Allow real-time online condition monitoring of two key fault gases (H2 and CO). Hydrogen (H2) is involved in nearly every fault of the isolation system of power transformers and Carbon Monoxide (CO) is a sign of cellulosic/paper insulation breakdown. With HYDROCAL 1003 analysing the transformer oil the transformer can maintain a long and trouble-free service life.

The HYDROCAL 1005 (offshore version available)

Individually measures four key fault gases (H2, CO, C2H2 and C2H4) dissolved in transformer oil. An increase in Acetylene (C2H2) and Ethylene (C2H4) further classifies the nature of the fault as overheating, partial discharge or high energy arcing. This extra data from the HYDROCAL 1005 reduces the amount of maintenance time because the probable cause of any faults will have been established before action takes place.

The HYDROCAL 1008 (offshore version available)

Individually measures seven key fault gases (H2, CO, CO2, CH4, C2H2, C2H4 and C2H6). The additional monitoring capabilities of Methane (CH4), Ethane (C2H6) and Carbon Dioxide (CO2) allow incipient faults to be further pinpointed and anticipatory resources to be applied effectively. The Hydrocal 1008 is also available in an enclosure especially designed for use offshore.

The HYDROCAL 1009 (offshore version available)

Individually measures eight key fault gases (H2,O2, CO, CO2, CH4, C2H2, C2H4 and C2H6). The additional monitoring capability of Oxygen (O2) allows for the detection of excessive aging or leakages within the sealing of hermetic transformers.

Multi-Gas-in-Oil Analysis Systems with Transformer Monitoring Functions

In addition to the main HYDROCAL units, MTE also manufactures Multi-Gas-in-Oil analysis systems with transformer monitoring functions. These units are based upon the HYDROCAL 1005 and 1008 units and are designed for multi-gas-in-oil analysis on a bank of three adjacent single-phase transformers.

The HYDROCAL 1005-3/-2/-1

This wall mounted system allows for the measurement of Moisture in Oil (H2O) and the key gases Hydrogen (H2), Carbon Monoxide (CO), Acetylene (C2H2) and Ethylene (C2H4) dissolved in transformer oil.

The HYDROCAL 1008-3/-2/-1

This wall mounted system allows for the measurement of Moisture in Oil (H2O) and the key gases Hydrogen (H2), Carbon Monoxide(CO), Carbon Dioxide (CO2), Methane (CH4), Acetylene (C2H2), Ethylene (C2H4) and Ethane (C2H6) dissolved in transformer oil.

Tap Changer Monitoring

The MTE HYDROTAP is designed for multi-gas DGA analysis on tap changers and transformer tanks.


This wall mounted system allows for the measurement of Moisture in Oil (H2O) and the key gases Hydrogen (H2), Carbon Monoxide(CO), Carbon Dioxide (CO2), Methane (CH4), Acetylene (C2H2), Ethylene (C2H4) and Ethane (C2H6) dissolved in transformer oil.

On-line Transformer Monitoring Extension Package

As an addition to the HYDROCAL range, MTE offers the HYDROCAL MS-7 extension package which offers transformer thermal condition monitoring. For additional monitoring of top oil, bottom oil, tap changer oil and ambient temperatures in addition to the load current, load voltage and tap changer position.


Complete on-line transformer monitoring extension package including cabinet, cable glands, power supply, circuit breakers, thermal connectors, anti-condensation heater, transducers, connection cable, transmission cable, and wiring diagram.

Bushing Monitoring

The ZVCM-1001 is a permanently installed online bushing monitor extension package for the HYDROCAL 1005 and 1008 gas-in-oil analysis systems.

ZVCM-1001 Bushing monitoring

Continuous measurement of up to six leakage currents, testing of power factor and capacitance values and monitoring of bushing condition, capacitance coupled voltage transformers (CCVTs) and free standing current transformers (CTs).