Online Partial Discharge Monitoring

Online Partial Discharge Monitoring

When the insulation in power cables and its accessories like terminations and joints deteriorates, partial discharge occurs. If not monitored and fixed in time, it can lead to power outages and expensive repairs. Partial discharge can be caused due to particles, cracks, voids and such weak spots in the internal insulation of the cable. If installation is not performed properly also, the cables, its terminations and joints can get damaged at that time.

Using appropriate sensors, we can monitor and trend partial discharge, and this can be done in two ways: temporary monitoring, where periodic monitoring is conducted, or continuously, throughout the equipment’s operating life. The main points of measurement are the joints and terminations of cables. Sound is the first sign that there is something wrong; In fact, even if the components start heating up, they emit some sound. If the sound is properly isolated and interpreted, it can convey if there is any risk and if action needs to be taken. For effective localization of detrimental partial discharge phenomena, the testing equipment uses partial discharge separation algorithms and robust noise suppression.

At Ocean Technical & Mechanical Services LLC, we use the best-in-class equipment to carry out partial discharge testing. We rely on equipment from IPEC Ltd, the leading manufacturer of these devices.

We mainly use the ASM or Advanced Substation Monitor from IPEC for monitoring power networks of our customers. Thanks to the superior monitoring technology of IPEC systems, our customers have peace of mind as we are able to secure their assets through continuous monitoring. The monitoring systems provide robust data analytics, sophisticated noise rejection and high-res data collection to identify PD so that it can be fixed before it becomes problematic.

We use the following equipment to deliver optimal online partial discharge monitoring services:

PD Alarm

This is mounted on assets to catch PD in transformers, RMUs and high-voltage switchgear, and is ideal for small substations. It triggers alarms, both remote and local, along with local indication. It is covered in a sturdy case that can be mounted on the RMU magnetically. It’s a user-friendly system and installation (no wiring needed) and with an integrated modem, can be configured to set off remote alarms. Its algorithms separate PD from noise for accurate results. It displays alarm history along with the present ones, and the ultrasound and TEV levels are displayed in decibels. TEV is the electrical transients generated due to internal PD. 3 separate channels help detect and track surface PD.


  • With early warning feature about defects, it helps avoid power outages and failure
  • Its design is suitable for large scale implementation across distributed assets making it economical.
  • When deployed as part of a maintenance program, it can help prevent failures

ASM Online PD Monitoring Systems

These systems allow continuous monitoring of PD in substation assets like switchgear, cables, GIS, and more, and are suitable for EHV, HV, and MV equipment. The ASMTM is a boon for asset managers as they provide real-time data on equipment condition, accessible through iSM, a secure website that’s client-specific, and can be accessed without internet if there is integration of server with client network. It can be deployed in industrial networks and distribution substations. A range of ASM products are available to suit varied network requirements and layouts: Portable, Remote, Mini, and Central. All these are compatible with the PD sensors from IPEC, like the high-frequency CTs that monitor cable health, and sensors to monitor condition of transformers and switchgears, humidity, temperature, and pressure sensors that monitor the environment, and UHF sensors that monitor GIS conditions. The PD measurements are downloaded automatically onto a central server, and stored in robust databases. Users can access it through the iSM website. Alarms are sent via SCADA, SMS, and email.


  • With PD sensors that are connected to the HV network, the ASM detects PD online non-intrusively, eliminating the need for disconnecting circuits.
  • The 19” outer cabinet enables customization like UPS, integrating with current equipment, and cooling. 
  • As it downloads to a central database, it has remote accessibility via smart devices.


This is used for medium term testing of PD in switchgear and cables, for 4 weeks or more in a substation. It provides information about the plant assets which may have had high PD levels in a spot test, and managers can decide about implementing a temporary monitoring system to ensure short-term asset health.


  • Weighing only 24 kg, it can be easily carried an installed to any site
  • The monitor is secured in a sturdy IP rated carrier case with handle
  • It can be configured to monitor systems for short or medium terms.


The Mini is used for permanent monitoring of PD in switchgear and cables, and has complete functionality of the ASM series in a smaller version. It is suitable for applications that have fewer sensors.


  • It is sturdy and light, and is wall mountable
  • Integrated wireless communication modules that allow swift connection to central servers
  • Compact design allows a max of 4 sensors, integrated with UHF, TEV, HFCT, or ultrasonic sensors from IPEC.


This PD monitor is used in distributed assets in a site or across networks. It is suitable for use in harsh environments like joint manholes and EHV cable tunnels. Fiber optic links the systems together for easy monitoring. 


  • It can be configured with a maximum of 20 channels and installed in industrial environments.
  • It’s an economical solution for large scale deployment of monitoring systems across large sites in multiple locations and in EHV circuits, with data sent back to central servers.


Continuous testing and monitoring of cables and switchgear is performed with this device, the Central offers rapid data collection and analysis, This is the most widely implemented monitoring system in substations globally.


  • Precise, automated PD assessments of assets
  • Design is ideal for monitoring entire substations
  • 128-channel capacity can be combined with ay IPEC sensor
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