GISmonitor - Partial Discharge Monitoring System
On-line PD monitoring of gas-insulated switchgear
On-line PD monitoring of gas-insulated switchgear
Key Benefits
- Parallel UHF PD measurement on all channels
- Centralized architecture
- High level of redundancy
- Highly extendable
Description
When it comes to Partial Discharge (PD) monitoring, Power Diagnostix’s GISmonitor is the perfect choice for the job. The main task of the GISmonitor is to provide the user with a reliable Partial Discharge Monitoring System (PDMS) capable of detecting defects hidden inside the Gas Insulated Switchgear (GIS) such as hopping particles, floating potential, cracks in insulators, protrusion or other degradation in the insulation system. The system’s hardware has been optimised for continuous, parallel and real-time PD acquisition in order to record each signal coming from the pre-installed UHF sensors inside the GIS enclosure, no PD activity is left undetected.
The Frequency Converter Units (FCU2) pick up the UHF signal from the embedded UHF sensor and demodulates it into a lower frequency band for easy transmission over longer distances. Special Input Protection Units (IPU2B) placed at the output of the UHF sensors block strong signals, such as very fast transients (VFT), and protect the PDMS.
Each UHF sensor is connected to an acquisition cabinet (PDMAR) that process the data before sending it to the control cabinet (PDMCR): each of these acquisition units can be connected up to 120 UHF sensors. With very few acquisition cabinets, Power Diagnostix’s GISmonitor can therefore cover even the largest GIS and thanks to its modular approach it is highly extendable in case of future extension of the switchgear.
The acquired and processed data is sent through fiber optic ring network to the control unit (PDMCR) where the user can directly operate and have a complete overview of the status of the GIS. In order to ensure that a proper analysis of the measured PDs can be conducted, the GISmonitor software provides the user with a various set of features and options. Through a monitoring mode the operator can access to the historical and live analysis of years of measured data in just a click while also checking the PD event list that summarizes the most critical acquired signals. All the data is collected, stored and automatically analysed in one central server and a database for automatic recognition of particular defects is provided (ICMexpert).
Dedicated features for pre-energization activities are part of the GISmonitor software. A Sensitivity Verification mode, with CIGRE TBA 654 compliancy, reduces to a minimum the requested time for the commissioning of the PDMS and automatically generate a report for the customer. The sensible HV Test that is performed before the energization of a GIS is supported by a dedicated HV Test mode that allows the user to record PD levels and applied voltage simultaneously creating therefore a replay that can be viewed anytime: this constitutes a fingerprint of the substation at the moment of the test.
The PDMS generates and forwards alarms to the subordinated system, such as SCADA, in the exact moment as they are raised, through different interfaces such as potential-free relays or IEC61850 communication protocol.
In case the GIS to monitor is not provided with embedded UHF PD sensors, Power Diagnostix can offer also a series of accessories and external sensors optimized for retrofitting.
To receive software updates or user guides, please contact support.pdix@megger.com or call +49 241 74927. Please have your device serial number ready or state your reason for interest.
Frequently Asked Questions
Which special features or capabilities of a GISmonitor make it more suitable for detecting PD in a GIS than other PD monitoring solutions?
Certain features set the GISmonitor apart in its abilities as a specific PD monitoring system for GIS. These differentiating features include: The unit accommodates a customised system layout for each installation The flexible system design due to frequency conversion allows a centralized structure and limits the number of acquisition units on site reducing drastically also the number of possible failure points during operation Due to the modular concept of Power Diagnostix the PDMS can be easily extended with more channels in case of extension of the GIS Advanced and dedicated software features for sensitivity verification and HV Test developed with feedbacks of on-site and commissioning engineers from GIS OEMs High levels of redundancy and self-monitoring Highest cyber security standards (hardened system, encrypted communication, user authentication, integration to superordinate systems) Continuous and parallel PD measurement on all channels, no PD pulse gets lost All PD measurement data is saved and stored through an optimized memory saving algorithm on the control cabinet. In-depth review and analysis is therefore facilitated The provided PD database for automatic recognition is extendable, therefore the system gets stronger and more efficient with every new PD pattern saved The operator has various options to interact with the PDMS, including remote access facilities, IEC61850, or web based access. More features often necessitate more hardware. When choosing between multiple PD monitoring systems for your GIS, look closely at the prospective systems' specific capabilities to ensure they are comparable.
What criteria should make me consider a GISmonitor over a GISmonitor Portable?
The continuous data acquisition, storage, and analysis provide a complete overview of the development of PD activity within your switchgear. You can track ageing mechanisms and evaluate the urgency of taking action based on continuous data acquisition. Furthermore, a permanent PD monitoring system provides an instant indication in case PD activity occurs. Manual measurements with a portable instrument can be weeks or months apart, possibly delaying detection after PD's inception.
What do I have to do if I have more than 120 UHF sensors to connect?
The GISmonitor is based on a scalable and modular architecture. The number of channels can be increased by adding more acquisition cards in the PDMARs and, if required, more PDMARs themselves. With this approach, systems with more than 1000 channels are possible, and a system design customised and optimised for a specific GIS can be provided.
I am relatively unexperienced in PD testing. How can I become proficient in detecting PD activity when using the GISmonitor?
The detection of the problem is done by the GISmonitor system autonomously. You will not be required to determine if there is PD activity. The software algorithm continuously analyses all measured data and detects whether PD activity is present. Regarding a deep analysis of a PD defect, our ICMexpert software comes with a database of known defects. The software automatically takes the phase resolved partial discharge (PRPD) that triggers an alarm, compares it to a database of known defects and finds the best match within our database. Accordingly, it will give you an indication of the most likely type of defect you are facing. If you want you can also store the just measured PD pattern and add it to the database itself: next time you are on site you will have one more measurement to use as a reference for the automatic recognition! In this way you can build your own database that will come in hand each time you have to perform an on-site measurement/activity.
When it comes to GIS monitoring I don’t see any measured value in pC. What am I missing?
According to the extremely important CIGRE TBA654 “UHF partial discharge detection system for GIS: application guide for sensitivity verification” document: “For the UHF method a calibration to “apparent charge in pC” is not possible due to the complex PD pulse propagation characteristics”. Therefore the measurement data is reported either in dBµV or dBm. Power Diagnostix suggests to everyone who is approaching UHF measurement on GIS for the first time to download such a document from CIGRE website.
