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Partial discharge (PD) monitoring in high voltage power plants is a useful tool to detect the presence of insulation degradation in the electrical systems [1]. Specifically, condition assessment of power systems has the advantage of reducing maintenance and repair costs, downtime and reducing risks. This requires measurement of field PD signals which are often observed in an environment contaminated...
This paper investigates correlations of Partial Discharge (PD) measurements of associated statistical parameters from phase-charge-number Φ-q-n plots from IEC60270 PD measurements and High Frequency Current Transformer (HFCT) Φ-peak-n plot PD measurements. These are also compared with Electromagnetic Interference (EMI) Radio Frequency (RF) measurements. The three methods record simultaneously PD activity...
Selected mapping (SLM) is an effective method for addressing high peak-to-average power ratio (PAPR) issues in orthogonal frequency division multiplexing (OFDM) systems. However, the standard SLM approach introduces additional data decoding challenges in the form of side information (SI) transmission and estimation. In general, SI transmission reduces data throughput and SI estimation normally involves...
This paper studies control format indicator (CFI) estimation methods in 4G-LTE communication systems. CFI is an essential control signal in LTE, and must be correctly detected at the receiver to avoid degraded system performance. The standard method of CFI detection involves the use of the Maximum Likelihood (ML) estimation criterion. Unfortunately, ML decoding performance relies on accurate channel...
This paper addresses the issue of high computational complexity associated with side information (SI) estimation in orthogonal frequency division multiplexing (OFDM) systems that implement selected mapping (SLM) to reduce peak-to-average power ratio (PAPR). The proposed method is based on a slightly modified SLM approach that enables the use of a low complexity binary detection criterion for SI estimation,...
To reduce the occurrence of high peak-to-average power ratio (PAPR), this paper introduces prolate-binary sequences, and their application in orthogonal frequency division multiplexing (OFDM) systems that implement selected mapping (SLM). Through computer simulation, it is shown that the proposed prolate-binary sequences offer combined improved PAPR reduction performance, and reduced computational...
This paper presents simultaneous measurements using three methods of partial discharge detection on 15kV high voltage cable sections with artificially created fault geometries, namely a semiconductor point and a large and small metal particle embedded on the insulation. These faults are simultaneously investigated using two 20MHz bandwidth HFCTs and an IEC60270 system. The peak value of one of the...
This paper presents experiments carried out on sections of typical subsea llkV HV cable with an artificially created fault geometry, namely a semiconductor point fault which is then compared to a clean termination (no point fault) with the fault removed. Partial Discharge (PD) measurements using IEC60270 phase-charge-number (PQN or (Ф-q-n), peak High Frequency Current Transformer (HFCT) (Ф-q-n, Low...
This paper compares single network (SNN) and ensemble neural network (ENN) capabilities to recognize and distinguish surface discharges between two pointinterface-pressboard arrangements with point angles of 100 and 450. The training fingerprints for both the SNN and ENN comprise statistical parameters from the measurement of the surface discharge patterns captured over a period of 15 hours. The results...
High voltage bushing faults represent over one quarter of power transformer failures, therefore their reliability is crucial. The monitoring of partial discharge (PD) activity within a bushing to provide early identification of faults is well known. This paper provides a comparative analysis of three different techniques commonly used for PD measurements in bushings. Over time, concurrent PD measurements...
This paper presents an initial investigation on the effect of an external magnetic field on partial discharge (PD) characteristics of voids in solid dielectric media, with a particular focus on statistics parameters derived from the classic phased-resolved patterns. Although it has long been known that high magnetic fields are present in equipment such as power transformers where PD may occur, only...
Gas filled cavities in solid insulation can form during production and are likely to have initial spherical or ellipsoidal geometry; as degradation takes place the shape will distort. Due to the difficulties of producing spherical and ellipsoidal cavity shapes most previous partial discharge (PD) measurements, in polymeric insulations, have used a layered polymer sandwich approach to create flat cylindrical...
Moisture ingress within a high voltage power transformer bushing can be detrimental to the insulation and causes the majority of bushing failures. In practice, wet bushings are known to have moisture accumulate within the lower region of the condenser. However, traditional power frequency measurements are often too insensitive to adequately evaluate these moisture conditions. Variable frequency analysis...
Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. They are degraded however when they are subjected to partial discharges (PD). Factors which control the PD activity include pressure and type of gas present. The pressure variation in a self-contained void will differ from that in voids with channels; also a void with a channel connected...
Within a high voltage substation, power transformer bushings are key components and an assessment of their condition is important to ensure operational reliability. Bushings represent a large proportion of transformer failures, where most issues are as a result of moisture ingress. Moisture ingress affects the distribution of the electric field and changes the capacitance and dissipation factor (tanδ)...
This paper details the use of Pulse Sequence Analysis (PSA) on sequentially captured PD activity within artificially created voids in Polyethylene Terepthalate (PET). Tests were undertaken using three void defect configurations, i.e. a single void, two voids in series between the HV electrodes and two voids in parallel between the HV electrodes. Supply voltages close to the inception point for each...
This paper presents a real-time implementation of partial discharge (PD) signal de-noising based on wavelet analysis. The results show that the Second Generation Wavelet Transform (SGWT) removes effectively white Gaussian noise (WGN), requires a smaller footprint and is less computationally intensive than the Discrete Wavelet Transform (DWT), reducing the cost for the hardware implementation. It is...
Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. These materials are degraded however when they are subjected to Partial Discharge (PD). Factors which control the PD activity include pressure and type of gas present. When PD occurs in insulation pressure is created and gaseous products changed due to the energy input. A series of experiments...
A numerical model to simulate a partial discharge within a bound cavity is presented in this paper. The partial discharge inception voltage and current pulse characteristics are established numerically and compared against experimental tests. The defect geometry used in this work is associated with a high voltage transformer bushing, namely a cavity formed between a punctured aluminium grading foil...
Partial discharges (PD) are electrical discharges which occur when the insulation system of electrical equipment under high voltage stress starts to break down. Radio frequency measurement methods can be employed to detect the radiated energy from the PD activity and therefore locate the PD source. Based on suitable arrangements of multiple antennas and measured time-differences-of-arrival (TDOA),...
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