Transformer monitoring

The importance of a power transformer that needs to receive a grid power supply and transform it into a useful voltage level can not be emphasized enough.

Transformers belong to one of the most critical equipments that has to maintain a continuous power supply in order for production to operate. In case such equipment fails, the loss of power supply to consumers means critical breakdown.

Having equipment reliability data helps with an assessment of the overall reliability of an electric system and in combination with the analysis of past failure data, future failure behavior can be reduced.

The transformer monitoring system (TMS) is built with a clear goal - to help its users improve asset management and prevent critical equipment from unplanned shutdowns. With over 500 systems installed around the globe, the TMS system sets the standards in transformer monitoring.

The transformer monitoring system is an object-oriented system (SCADA system – process-oriented system). It provides insight into the state of a transformer and its real-time service conditions. The system uses several key functions such as:

  • measurement of quantities
  • estimations based on measured values and transformer data (algorithms)
  • comparison of current and initial values (trends)
  • comparison of current values with those obtained from a model (model monitoring)

The worldwide transformer reliability survey conducted by CIGRE WG A2.37 and published in Brochure no. 642, collected and analyzed 964 major failures which occurred in the period 1996 to 2010, within a total population of 167,459 transformer-years, contributed by 58 utilities from 21 countries.

The results point out the main causes of transformer failures, including the reasons with the most severe results such as fire or explosion. it was concluded that failures were predominantly winding (40%) and tap changer (27%), while MV and LV bushings, lead exits, and core showed smaller contribution levels. As seen from the survey results HV Bushings significantly also contribute to large failures, which means that operators should place a large focus on bushing monitoring.

Many recent studies have shown that bushing failure is one of the most common causes of transformer failure. Thus the need for bushing diagnostic and monitoring systems has risen. Although the offline diagnostic gives more accurate and precise insight into the bushing insulation state, it is still not common practice for substation maintenance to perform such tests very often. The main reason is that it demands transformer outage, well-trained personnel, and expensive equipment.

KONČAR TMS bushing monitoring provides insight into the bushing insulation state while the transformer is online. A developing fault inside the bushing can now be detected in the early stages so proper action can be taken to save substation equipment and personnel. The powerful digital signal processor module enables precise measurement of bushing leakage current amplitude and phase angle. By measuring those parameters, relative dissipation factor (△ tan δ) change and relative capacitance change (△C/C0 ) can be calculated.

Key features:

  • Bushing capacitance and tanδ monitoring
  • Bushing adapters for various tap design
  • Voltage RMS, Peak measurement
  • Overvoltage detection
  • Frequency and phase measurements

Three types of bushing methods to choose from:

(1) VT reference method; (2) Dual transformer method; (3) Sum of currents methods



  • For medium-sized transmission and distribution power transformers
  • Monitoring scope includes: HV Bushings; Active part (gas and moisture in oil, thermal model, paper insulation)


  • For Large power and Generator Step-up Unit transformers
  • Monitoring scope includes: TMS mini,  MV and LV bushings, Partial discharges, OLTC,  Cooling system


  • For HV and UHV transmission S/s
  • Monitoring scope includes: TMS standard, transient overvoltages

TMS is equipped with advanced tools that allow quicker and more effective data management

  • Trend analysis - allows data selection from past periods and comparison of data in a single graph
  • Alarms and events logging - list of all situations when problems occurred with more information
  • Loading forecast - a tool that enables estimation of a possible transformer overloading, depending on a current transformer state and overloading needs.
  • Data export to text and Microsoft Excel - the information can easily be shared and additionally analyzed
  • Automatic report generation - a creation of specific reports for target people based on their area of interest

In order to target the biggest issues of transformers and help customers choose the appropriate TMS option, we also offer the following services

  • Consulting services on how to select the optimal monitoring system for a new or an in-service transformer
  • Installation and commissioning
  • Staff training
  • Recommendation of limit values (alarms) settings
  • Expertise in the interpretation of the acquired monitoring results

Solution benefits

Fault detection

Monitoring and diagnostic for all vital transformer parts
Prevention of failures and unplanned outages
User-defined alarm limit and gradient setting



Applicable to all types of power transformers and shunt reactors
Fits new or existing transformers from any manufacturer


Condition-based maintenance

Optimization of transformer performance
Improved asset management using overloading and lifetime expectancy estimations
Integration of data for root cause analysis


Expert functions

Advanced trending analysis tools
Interpretation methods of fault gas analysis according to relevant IEC and IEEE standards
Long term data archive with event logging
Automatically generated reports for stakeholders


Next steps

See for yourself why TMS is the right solution for you by choosing one of the options below or simply contact us.

Brochure: Transformer monitoring system

Learn more about the Partial discharge measurement and monitoring system -  complete monitoring solutions for every type of asset or automated laboratory measurements which is an integral part of the transformer monitoring system Končar TMS.

Partial discharge measurement and monitoring system - iPDCore

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