Products

4 Channel Digital Partial discharge System

HVS 2000PDD/T		HVS 1000PDD/T
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The instruments can be used for both on-line and off-line (conventional) PD testing of high voltage plant. The high voltage connections, coupling capacitors, and power supplies necessary for off-line testing are not included in the scope of supply of the instrument, and are not covered in this document.

The instrument as been designed to be a general-purpose diagnostic tool for making measurements on up to 4 channels simultaneously. The system will cope with a wide range of sensors and measurement conditions and makes an excellent and portable replacement for conventional discharge detectors.

The PD Gold software, which interfaces with and operates the built-in digitizer, is very simple to operate, and is designed to be intuitive to provide the user with a powerful tool for making PD measurements.

The PD Gold software displays the PD information across the complete 360^o phase of the power cycle, so that the familiar discharge patterns can be observed in real time. Whilst the system shows real time PD events it is recommended that PD measurements made in the field are recorded are stored over a given time interval (typically 5 to 10 minutes) to provide statistical, post-analysis of the PD data to be made using the the PD Gold Software.

The system can be calibrated (through the use of any PD Calibrator) to read results in pC’s (Pico Coulombs) and calibrations can be made for all of the 4 channels separately, if required. The calibration process has also been designed to be a simple and intuitive process.

Compared to this it does enable all types of conventional PD measurements to be made on all 4 available channels.

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16 channel Multiplexer Type 981M

The unit is designed to be used in conjunction with the Digital PD instruments Types HVS1000-2000 PDD/T The multiplexer is operated from the Digital PD unit using the PD gold software supplied . In this way up to 16 channels of data can be monitored using the Digital PD instruments.

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High Voltage Coupling Capacitors

• For direct connection to high voltage systems providing signal coupling from the test circuit. Coupling capacitors can be supplied up to 100 kV rating.
• Rating up to 40kV the capacitors are compact ceramic type.
• Rating up to 100kV the capacitors are conventional paper/polyester type.
• Both types give less than 5pC inherent discharge level

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PD Calibrator

• Calibrator Type HVS 998/0011
• Hand held battery operated
• Provides 4 outputs 10nC, 1nC, 100pC and 10pC

Radio Frequency Current Transducers Rogowski Coil - Air Cord

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A number of designs of radio frequency current transducers based on the Rogowski Coil principle are available. These are primarily designed for use in measuring high frequency current pulses such as those generated by electrical discharge processes. As the transducers are based on an air cored principle, they are not subject to the usual limitations of saturation and non-linearity of the wide band ferrite current transformers. Thus they can be used to measure rf current signals and reject low frequency currents when installed on cables and bus bars carrying large cur currents

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Radio Frequency Current Transducers Rogowski Coil - Ferrite Split

A number of designs of radio frequency current transducers based on the Rogowski Coil principle are available. These are primarily designed for use in measuring high frequency current pulses such as those generated by electrical discharge processes. These transducers are manufactured using ferrite type cores thus giving high sensitivity for use in monitoring low level PD activity. They are limited for use in medium current applications upto 200Amps.

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Traditional (since 1970’s) on-line measurements have been made using TEV (Transient Earth Voltage) measurements. These are small Radio Frequency (RF) Aerials which detect the high frequency PD pulses emanating from the discharge site in the switchgear. These pulses tend to have pulse widths of a few tens of nanoseconds, and act as a good medium for non-intrusive PD detection in switchgear. Detection of these pulses can also be used for localisation of the PD site. The Transient Earth Voltage (TEV) Sensor is recommended for this application. The Sensor is magnetically latched to the earthed, metal-casing of the switchgear panel and can therefore be used for on-line testing.

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A Partial Discharge (PD) mapping system

Partial discharge (PD) mapping is currently the best way of estimating service performance of high voltage insulation in cables. For high voltage cables, no published criteria exist for the PD parameters which can be used as an ‘alarm level’, but several utilities are trying to establish exactly this. The PD mapping system is designed to locate the sites of PD along a high voltage cable, and display the data in an easy and understandable way.

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Cable Mapping Transponder Unit

The battery operated Cable Mapping Transponder Unit is used for PD location on installed cables. For PD location, the reflected pulse which has bounced from the far end of the cable is required for the location. For some simple cable circuits, and for all more complicated circuits, the waveforms of PD events can not be easily interpreted, and the reflected pulse is difficult to distinguish. Hence if the pulse arriving at the end of the cable is used to trigger a device which can apply a larger pulse to the cable, then this pulse can be used to carry out the location instead of the small unclear pulse which is naturally present in the cable

The transponder provides an output pulse height of 200v nominal peak into a high impedance, or 100V nominal peak into 50 ohms.

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Pulse Generator for TDR measurements with Cable mapping equipment

The generator feeds a short duration current pulse into the cable through the coupling device. The reflected pulse is then displayed on the PD monitor and the delay calculated to obtain the cable characteristics. The value of this delay in μSec is then used in the Data Input window of the cable mapping software.

Radio Frequency Monitor Alarm Unit

The Unit is designed to capture the Rf activity created by partial discharges occurring within large transformers and give a dc level and a 4-20mA output representing this level and also produce an alarm when a threshold has been exceeding. Both the dc level and the alarm status can be used by a system giving overall condition monitoring of the transformer.