OSM-Longshot Software Modules

The OSM-Longshot units are supplied with the following 2x PD Software Analysis programs pre-programed into their built-in PC's as standard:

• PDGold© for data acquisition and storage using the OSM-Longshot unit
• PDReader© for post-processing, analysis and reportage of the data collected

The PD Reader© Software Module is also provided in a PC-Compatible Format which can be installed on any PC owned by the customer, thus enabling post-test analysis of the data collected by PD Gold© in the substation to be carried out at the office whilst the Longshot unit is kept in the field where it is best placed, collecting PD data.

Additionally to the above standard modules, if the user wishes to perform on-line PD Mapping (Location) on HV cable feeders with the IPEC/HVSL Portable Transponder System, then they can add the PD Map© Software expansion software.

All of these OSM-Longshot software programs run on operating systems Win 2000, Win XP (home and professional) and are compatible with MS Office for report generation.

PDGold© PD Acquisition Software - Main Page

The PDGold© program (Main Page shown right) contains all the functions that allow control of the OSM-Longshot instrument, to set the correct values of the acquisition parameters, to acquire and visualise the PD dataset in order to get an immediate diagnostic response.

The PDGold© software collects the PD data in 200x 'slots' across the 50Hz (or 60Hz) power cycle, one cycle at a time, followed by a processing stage of a few seconds, followed by the acquisition and processing of a second cycle and so on. Each signal acquired is synchronised by the AC mains voltage waveform supply (or other volatge signal).

The software thus allows the user to observe this 360° plot of the PD behaviour showing both the individual 20ms 'shots' and the cumulative measurements of all those taken up to that point, in 'real-time'. For the standard PDGold© measurement this would be left to run typically for 3 to 5 minutes with around 100 to 200 individual power cycles usually saved.

PDGold© - Advanced 'Waveforms and Segments' Measurements

The standard PDGold© measurement described above provides the user with a measurement of the cumulative, phase-related discharge pattern of the HV plant under test, using the 'slot detector' method described. Whilst this standard measurement will inform the user, in most instances, whether or not there is discharge present, it will not provide any information on the PD pulse shapes, their type or likely source. To obtain this information the user can utilise the automatic 'Waveforms and Segments' detection module in the PDGold© Software.

The PDGold© Software Waveforms and Segments acquisition program collects the top 20 pulses ('Segments') from each power cycle recording. These represent the highest pulses (PD and Noise) from across and it is these pulses which are investigated further in the PDReader© 'Event Recogniser' module. As 20xSegments are collected on every 20ms power-cycle acquisition by the PDGold© it will require a short period of time to obtain a statistically valid sample (IPEC/HVSL recommend the user acquires between 200 and 500 'Segments' in order to provide a statistically valid data-set for the PD Phenomena present).

PDReader© Software - Main Page

PDReader© allows the data files acquired using PDGold© to be both read and then processed for in-depth analysis of the detected PD phenomena.

On completion of the PDGold© acquisition and the recording of the data into a PDGold© datafile the user can immediately view the recorded data using the PDReader© software. The Main Page of the PDReader© program is shown right.

Two main plots can be observed, the Top Graph shows the measured activity over the period of the test (10 minutes in this example) and the Bottom Graph shows the cumulative phase-resolved data from the several hundred 20mSec power cycle waveforms which have been collected.

PDReader© Software - 'Event Recogniser' Analysis Module.

PDReader© - Event Recogniser Analysis Page Showing Cable PD

The Event Recogniser Analysis Module (see right) provides analysis and reporting on the PD activity within the waveforms collected, providing a complete breakdown of all of the PD and noise pulses (the 'waveforms').

A feature extraction procedure within the software allows data size reduction for the classification purpose while keeping the pulse shape information. By classifying pulse features in the system it is able to classify properly all the pulses in the different clusters and derive the relevant sub-patterns.

The module automatically pre-sorts each pulse 'Segment' collected (typically 200 to 500 per measurement, providing the following information:

• Images of each pulse 'segment' from the main waveform
• PD Pulses measured in picoCoulombs (pC's)
• Statistical breakdown of events in the 4 x pulse categories in a 'Pie-Chart Format'
• Phase-related PD pulse plots, automatically pre-sorted into Cable PD, Local Equipment (Switchgear) PD and Noise Events (this uses PD pulse type 'knowledge rules' based on the frequency, risetime, falltime and shape of the pulses detected).

RF Noise Immunity Function

One of the main restrictions traditionally with on-line PD testing of HV plant is large amplitude, RF noise interference which can mask smaller PD events which exist under the noise signal. Conventional methods for removing noise have involved the Manual Noise Gating techniques which, when applied in the substation to continuous RF noise or powerline carrier noise tend to delete a large number of real PD events in the signal channels, making the final result meaningless.

Further to this restriction IPEC/HVSL have developed a software-filtering technique module within the new PDGold© v3.4 software. The software now includes a Radio Frequency (RF) Noise Reduction function which uses single frequency spectral subtraction to remove RF Noise from the measured signal. This is achieved automatically by the software.

PD Calibration in pico Coulombs (pC's)

The PDGold©/PDReader© Longshot software packages can provide on-line PD measurements directly in pC's (pico Coulombs) as standard as long as calibrated HFCT Sensors are used with the equipment. IPEC/HVSL supply calibrated, inductively-coupled HFCT sensors with a known Transfer Impedance to enable this to be carried out (link to sensors page).

For measurements on switchgear using TEV (Transient Earth Voltage) pick-up methods it is more usual to present discharge levels in terms of dB (decibel) levels which allows for comparison with dB guideline levels which have been used by the Electricity Association in the UK for over 25 years (refer to IPEC/HVSL for further details on dB Guideline Levels for MV Switchgear).

The calibration of the PD to be detected can also be carried out in the traditional way by measuring the PD levels of a known signal injected into the detection circuit. This can be done live, (using a high voltage calibration capacitor), or more commonly, with a low voltage two wire calibrator, with no applied voltage. This procedure results in the association of the dB level or mV level detected with a known number of pC's (Pico Coulombs). There are automatic calibration procedures available in the PDGold© Software if this is required by the user.

PDGold© Demo Software Module

The PDGold© and PDReader© software is supplied with a PD Simulator and Demo Software Module to allow the user to practice data acquisition with the system in the comfort of their office. It is recommended that the user by practices with the Demo Software Module to acquaint themselves with the functionality of the PDGold© and PDReader© software before the user takes the equipment to the Substation.

The Demo software module has been designed to provide the user with a tool to simulate various types of PD pulses (Cable PD, Switchgear etc) and also, as importantly, various types of electrical noise (Random Bit Noise and RF). The demo module is very sophisticated and the user can fine-tune the PD pulses and Noise in terms of magnitude, pulse width and rate. Once set-up the demo PD should then be recorded by the user using both the standard method and advanced PDGold© Data acquisition methods in order that the user can obtain practice in their usage. This can be done with a number of variations of PD types and Noise Types and will prove invaluable in providing a 'feel' for the types of signals which will be encountered in the field.

Printing and Copying from the PDReader© Software

Printing from the PDReader© Software on the OSM-Longshot unit can be achieved by connecting a printer to the unit using a suitable cable. The PDReader© Software has report pages incorporated in the software which allows the data collected to be displayed in a standard report format which can then be printed off as a single page document showing either full or partial waveforms and the relevant data associated with the waveforms. The user can use drop-down menus on the various pages in the PDReader© Software for copying individual waveform images into another windows document (e.g. Microsoft Word or Excel) for report purposes.