PD testing on transformers

HPD2000 series partial discharge detector measures partial discharge level of HV equipment base on impulse current principle as described in IEC60270 standard. The windows operate analyzer is designed to perform HV equipment partial discharge evaluation experiments. The analyzer adopts polymer dustproof protection case which is rugged and durable

● Meet IEC-60270 Standard, Measures PD level based on impulse current method

● Equip with internal and external utility frequency syntonization function

● Wide dynamic range with an auto-range gain selection

● Numbers of combinations for High pass filter and low pass filter

● Integrated PD level vs. applied voltage curve, for estimation of starting voltage and extinction voltage

● Integrated PRPS(phase resolve pulse sequence) graph, display PD level, phase, and time on a single 3D rendered graph

● Integrated PRPD(phase resolve partial discharge) graph, accumulating phase, PD repeating rate in time. With either log-log or decade scale

● Equip with RTSA(real-time spectrum analyzer), toggle between 1MHz to 10MHz. special graph persistence helps to locate noise frequency range and PD frequency range

● Equip with internal backup battery, automated shutdown when losing power

● Integrated full keyboard and touchpad mouse for editing report in the field

● Large 13.3” industry color LED, with good low temp performance

● Internal WIFI module provides real-time remote control customer service

● Automated report generation

Specifications

Sampling channel: independent two channel

Sampling rate: 12-50Msps each channel

Sampling depth: 16 bit

Time-base accuracy: 50ppm

Dynamic range: -40dB-60dB, auto/manual adjustment

PD range: 0.05pC-1000nC

Sensitivity: 0.1pC

Internal filter: high pass( 20kHz, 40kHz, 80kHz, 1MHz)

Low pass(150kHz,400kHz, 1MHz, OFF)

Test object capacitance: 6pF-25uF

Sensor: measurement impedance, HFCT

Nonlinear error: less than 3%

Test power frequency range: 20-500Hz

Communication: 2*USB, RJ45, WI-FI

OS: Windows &

Internal storage: 64GBSSD

Display: 13.3” LED 1280*720

Power supply: 90-264V AC, 47-63Hz

Environment：-20 to 50℃

Humidity ≤90%RH Non-condensing

Dimension: 405×335×190mm

Weight: 9kg

What is Partial Discharge ? why should we test for it?

Partial Discharge (PD) is an electrical discharge that occurs across a localized area of the insulation between two conducting electrodes, without completely bridging the gap (see IEC 60270). It can be caused by discontinuities or imperfections in the insulation system. Partial Discharge activity is an indication of an incipient medium voltage (MV) or high voltage (HV) insulation fault and is widely regarded as the best early warning indicator of electrical insulation deterioration in MV and HV electrical assets within power networks. In general Partial Discharge occurs in systems operating at voltages of 3 kV and above; however it should be noted that in some cases Partial Discharge can also occur at lower voltages (i.e. Variable Speed Drive / Variable Frequency drive motors and LV designs). Typical drivers for implementing PD programmers include; supporting Condition Based Maintenance (CBM), avoiding unplanned, often costly, outages and improving network reliability/uptime, increasing safety and extending asset life/delaying capital replacement (under OPEX budgets). The major advantage of On-line Partial Discharge testing and monitoring over off-line, is that it is non-intrusive, causing no interruption to service, and is performed under normal operating conditions (voltage, frequency, load and environmental), therefore no overstressing due to overvoltage.

Where does Partial Discharge occur?

Partial Discharge can occur at various points in the insulation system, for example: voids or cavities in solid or liquid insulation medium, at the interface between insulation layers such as delamination.

PD can be observed at various stages during the assets lifecycle. From the transportation, to the installation and commissioning of new equipment – often caused by improper installation or poor design and/or workmanship (particularly in cable joints and terminations which are made up on-site). Poor workmanship at the manufacturing stage of an asset can lead to premature failure, with a disproportionately high percentage of insulation failures being observed within the first 1–3 years of service compared to the rest of the working life of the asset. Referring to the bathtub curve below; Partial Discharge activity can start under normal working conditions in MV/HV assets where the insulation condition has deteriorated with age, or has been aged prematurely by thermal or electrical over-stressing, or due to improper installation.

Partial Discharge monitoring and asset management

On-line Partial Discharge monitoring allows for trends in activity to be observed over time. While PD is incepted by the high-voltage stresses, it can be influenced by the other operating and ambient stresses, for example; Load, Temperature, Humidity, etc. As PD activity is often present well in advance of insulation failure, by observing and understanding the PD over time it is possible to make strategic decisions about refurbishing and renewal programmers; including ordering and delivery of key parts with long lead times. Often it may not be necessary to replace an older asset which is perfectly serviceable, and thereby the capital replacement cost can be deferred through the use of electrical condition-based maintenance.

Partial Discharge testing and monitoring is particularly important when the medium or high voltage asset is critical to the operation of a network; this may be due to the asset’s age, limited network redundancy, past failures or the financial consequences of a failure. Qualification of PD criticality within the complete network can be achieved quickly and easily using HANDY technology to provide an early warning of any incipient insulation faults. Examples of MV and HV plant that can be tested/monitored include:

Cables and cable accessories (terminations, joints, sealing ends)

Switchgear (AIS, SIS & GIS)

Power Transformers and Bushings

Transformers (Oil Filled & Dry Type)

Rotating Machines Motors and Generators (including Direct On-Line & Variable Speed Drive or Variable Frequency Drive motors)

Instrument Transformers (Voltage & Current)

Capacitors

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