S. A. Bhatti

Estimation of Impulsive Noise in an Electricity Substation

Measurements of impulsive noise in a 400/275/132-kV electricity substation are presented. The measurements are made with three antennas having overlapping bands covering the range 100 MHz-6 GHz. This range includes those bands relevant to modern wireless local area network and wireless personal area network technologies (e.g., IEEE 802.11a/b/g and IEEE 802.15.1/4), which, if proved to be sufficiently robust in the presence of impulsive noise, could play a useful role in substation monitoring and control. Impulsive events are extracted from the measured data using the wavelet packet transform, and the statistical distributions of pulse rate, pulse amplitude, pulse duration, and pulse rise time are presented. An unexpected quasi-periodic component of the noise is observed.

Vulnerability of Zigbee to impulsive noise in electricity substations

The vulnerability of Zigbee technology to noise in an electricity substation environment is assessed. Substation noise obtained from a measurement campaign is modelled as a Symmetric α-Stable process. The parameters of the model are estimated from the measurements and the resulting model is used to investigate the likely BER performance of Zigbee technology deployed in a substation.

Laboratory Assessment of WLAN Performance Degradation in the Presence of Impulsive Noise

A laboratory test to assess the impact of impulsive noise on the performance of WLAN equipment is described. The test is put in the context of a larger programme of work to assess the performance and reliability of wireless equipment subject to partial discharge noise in high voltage electricity supply substations. The character of partial discharge and WLAN technology are briefly reviewed. The laboratory test methodology is reported and some preliminary results are presented. A related forthcoming field-trial for tests of WLAN equipment in a 275/400 kV air-insulated substation is briefly described.

Partial Discharge Location using Unsynchronized Radiometer Network for Condition Monitoring in HV Substations - A Proposed Approach

A location estimation system for online Partial Discharge (PD) detection is proposed as a low-cost approach to real-time condition monitoring, asset management and operation optimization in future smart grid. Some early progress in the development of subsystems (specifically the antenna, radiometer device, PD emulator and PD generator) for a proof-of-principle prototype system is described. The proposed PD Wireless Sensor Network (WSN) uses a novel approach to PD location which obviates the need for synchronization between sensors thereby improving scalability.

Performance simulations of WLAN and Zigbee in electricity substation impulsive noise environments

A physical layer performance evaluation of WLAN (IEEE 802.11b) and Zigbee (IEEE 802.15.4) receivers in the presence of impulsive noise is presented. Broadband impulsive noise is modeled as a Symmetric Alpha-Stable process. The parameters of the impulsive noise model are estimated from data recorded from an electricity transmission substation (ETS). The results show that the performance degradation of the Zigbee receiver is small whilst the WLAN receiver may suffer more significant degradation.

Wavelet transform processing applied to partial discharge evaluation

Partial Discharge (PD) is characterized by high frequency current pulses that occur in high voltage (HV) electrical equipments originated from gas ionization process when damaged insulation is submitted to high values of electric field [1]. PD monitoring is a useful method of assessing the aging degree of the insulation, manufacturing defects or chemical/mechanical damage. Many sources of noise (e.g. radio transmissions, commutator noise from rotating machines, power electronics switching circuits, corona discharge, etc.) can directly affect the PD estimation. Among the many mathematical techniques that can be applied to de-noise PD signals, the wavelet transform is one of the most powerful. It can simultaneously supply information about the pulse occurrence, time and pulse spectrum, and also de-noise in-field measured PD signals. In this paper is described the application of wavelet transform in the suppression of the main types of noise that can affect the observation and analysis of PD signals in high voltage apparatus. In addition, is presented a study that indicates the appropriated mother-wavelet for this application based on the cross-correlation factor.

Radio science and wireless communications for the smart grid

The smart grid paradigm is set to revolutionize electrical energy delivery over the next two decades. The advantages will be manifold but the challenges to realization will be correspondingly great and the cost will be large. The probable structure of the smart power grid is reviewed and contrasted with that of the traditional grid. The requirements of the communications component of the smart grid are outlined and the possible roles of wireless communication technologies highlighted. The electromagnetic environment in which smart grid wireless technology will have to operate is discussed as is the application of radio science to insulation condition monitoring and asset management of plant.

ZigBee performance in 400 kv air insulated power substation

An experimental assessment of the impact of the electromagnetic environment of a 400 kV substation on the performance of ZigBee equipment is described. The experimental assessment includes a pragmatic field trial and a laboratory test. The laboratory test, in which all external noise and interference are excluded, is used as a control. A simple set of metrics are used to compare the performance of ZigBee equipment deployed in the substation with that deployed in a controlled laboratory environment. The results based on more than 1.6 Gbit of transmitted data show no significant adverse impact of the substation electromagnetic environment on the performance of ZigBee equipment.