Powerlink Queensland

About: Powerlink Queensland is a company organization based out in Brisbane, Queensland, Australia. It is known for research contribution in the topics: Electric power system & Ethernet. The organization has 49 authors who have published 62 publications receiving 530 citations. The organization is also known as: Queensland Electricity Transmission Corporation Limited.

Optimisation of a sensor for onsite detection of partial discharges in power transformers by the UHF method

Abstract: Among the different solutions which allow onsite partial discharge measurement in energized power transformers, the UHF technique is gaining general interest. In order to apply this method in existing transformers, it is considered advantageous to design a UHF sensor to be fitted inside the transformer tank. This paper describes the constraints affecting the development of such sensor and the process followed to optimize its design. During this process, different solutions for broadband UHF antennas were analysed. The selection was based on computer simulation and experimental results. Computer simulation was used to evaluate differences in radiation pattern, antenna impedance, gain and effective area. Measurements of the antenna response to different partial discharge sources in oil were performed using an oil dielectric breakdown test set in an electromagnetic shielded laboratory. A group of selected antennas were then tested in a power transformer simulating the broadband signals generated by partial discharges by injecting controlled voltage pulses in the transformer. Finally, a sensor based on a conical monopole antenna structure was built and attached to a specially designed housing to be fitted inside the transformer tank through the drain valve. This final prototype was benchmarked during a high voltage factory test of a power transformer which showed a significant partial discharge activity.

Use of Precision Time Protocol to Synchronize Sampled-Value Process Buses

Abstract: Transmission smart grids will use a digital platform for the automation of high-voltage substations. The IEC 61850 series of standards, released in parts over the last ten years, provide a specification for substation communication networks and systems. These standards, along with IEEE Std 1588-2008 Precision Time Protocol version 2 (PTPv2) for precision timing, are recommended by both the IEC Smart Grid Strategy Group and the National Institute of Standards and Technology Framework and Roadmap for Smart Grid Interoperability Standards for substation automation. IEC 61850, PTPv2, and Ethernet are three complementary protocol families that together define the future of sampled-value (SV) digital process connections for smart substation automation. A time synchronization system is required for an SV process bus; however, the details are not defined in IEC 61850-9-2. PTPv2 provides the greatest accuracy of network-based time transfer systems, with timing errors of less than 100 ns achievable. The suitability of PTPv2 to synchronize sampling in a digital process bus is evaluated, with preliminary results indicating that steady-state performance of low-cost clocks is an acceptable 300 ns but that corrections issued by grandmaster clocks can introduce significant transients. Extremely stable grandmaster oscillators are required to ensure that any corrections are sufficiently small that time synchronizing performance is not degraded.

Observations of geomagnetically induced currents in the Australian power network

Abstract: [1] Infrastructures such as pipelines and power networks at low-middle latitude regions have historically been considered relatively immune to geomagnetically induced currents (GICs) Over the past decade there have been an increasing number of investigations into the impact of GICs in long grounded conductors at these latitudes The Australian region power network spans thousands of kilometers from low to middle latitudes The approaching maximum of solar cycle 24 and recent findings of studies into power networks located at similar latitudes have stimulated the Australian power industry to better understand this phenomenon in their region As a result, a pilot study to compare space weather activity with in situ GIC monitors at strategic locations within the power network was initiated This paper provides some results from the first of these operational GIC monitors during a modest geomagnetic storm, showing the first observational evidence of space weather well correlated with GICs measured in the Australian power network Transformer neutral currents show a high degree of similarity with the geoelectric field derived from the closest available geomagnetic observatory Current maxima of 4–5 amperes were observed in association with geoelectric field values of ~006–007 volts per kilometer This paper also discusses the GIC measurements obtained during this storm in terms of the space weather drivers and the considerably larger geoelectric field values anticipated during larger geomagnetic storms

Direct Evaluation of IEC 61850-9-2 Process Bus Network Performance

Abstract: This letter presents a technique to assess the overall network performance of sampled value process buses based on IEC 61850-9-2 using measurements from a single location in the network. The method is based upon the use of Ethernet cards with externally synchronized time stamping, and characteristics of the process bus protocol. The application and utility of the method is demonstrated by measuring latency introduced by Ethernet switches. Network latency can be measured from a single set of captures, rather than comparing source and destination captures. Absolute latency measures will greatly assist the design testing, commissioning and maintenance of these critical data networks.

Determining water in transformer paper insulation: analyzing aging transformers

Abstract: It is important to monitor the water concentration in the insulation of aging power transformers, because over time the insulation becomes wet, due to water ingress from the atmosphere and water formed in chemical reactions involving oxygen. If the water concentration is sufficiently high, the insulation will age prematurely [1] and the transformer may fail if overloaded [2]. In a previous article [3] we reported on the measurement of water concentration in the insulation paper of a power transformer that had been in service for only seven years. The waterconcentration data obtained using on-line water-activity probes were compared with corresponding data obtained from dielectric response measurements. In that work cellulose adsorption isotherms were used to process the water-activity-probe data. However, according to [4] and [5], inaccuracies in the waterconcentration estimates may result from the use of adsorption isotherms. According to [6], these inaccuracies may exceed 200%. The probable main causes are the transformer insulation materials not reaching thermal equilibrium, the water concentration within the insulation not being uniform, and variability in the properties of the insulating materials.