Electrical switching in a diakoptics based tram traction simulation tool and its implementation in a SCADA environment

Abstract

Safe electrical switching is a pre-requisite for secure and reliable operation and maintenance in any electrical utility and traction network. Electrical system safety regulatory bodies and corporate electrical regulations provide protocols including ‘no inadvertent system switching’ and are very strict regarding system safety policies and practices. An electrical High Voltage system ensures coded, legal and safe operational practices to achieve the required system safety, meeting, for instance, ‘on-time-every-time’ operational requirements. Every electrical entity needs to report their safe work practices in proper system safety documentation and effective coded demonstrations, and ensure safety through training-refresher programs to be accredited by technical commission and regulators. Electrical industries usually track real-time system parameters by remote monitoring, higher-level visual foot patrols, local-drone-online camera monitoring and preventative maintenance plans over the lifetime of the network system-switchgear maintenance regime. They undertake required maintenance and corrective progressive work with a systematically safe approach and in a documented manner. Safe electrical system isolation-restoration programs and effective workgroup safety is guaranteed by job specific risk assessment and job safety procedures. This thesis proposes an automated isolation-restoration switching method to be applied in the traction industry with special emphasis on system safety switching practices. It elaborates on how diakoptics, a mathematical method of tearing, stands out as one of the best methods to simulate and analyze a large-scale tram traction network. Examples based on traction systems in Adelaide, South Australia are used in this thesis as case studies on safe and effective isolation-restoration switching practices. The diakoptics algorithm splits a complex traction network into smaller pieces which are solved separately, and gets the optimized simulation of the whole electrical network in real time. Solutions of electrical subsections are combined to produce the correct representation of the entire network’s de-energized or energized switchgear state at a given time. The diakoptics - based ‘model tram traction simulator’ has been developed to cope with the system safety network switchgear orientation and system operational switching requirements. The model focuses on achieving electrical section-wise bottom to up topological power isolation, operational power restoration and entire network instantaneous electrical isolation-restoration in planned, unplanned and absolute emergency situations. A competent electrical operator, by working with the mimic of the traction simulator overhead and substation switchgear, can make an informed decision to progress. The on-duty electrical control officer updates the simulator to a system operational status. As the simulator switchgear connection-orientation mimics the real-time system switchgear operational state, the crew virtually makes a real-time patrol of the work location and the isolation limits, being able to plan safe maintenance work or prepare for a system upgrade. The system switching demonstrations, formally approved switching templates, related catenary system and detailed substation switchgear mimics which the maintainer requires are also included in the simulation tool. An automated isolation-restoration switching program to undertake any planned, unplanned and emergency maintenance work has been extensively tested and verified. The simulator has been upgraded to accommodate any future extensions and bypasses of the network. ‘One click’ immediate remote de-energization of the entire traction system has been included in the tool. Asset management, system safety management options, and system remote switching have been addressed. The tool is also capable of accommodating for future legislative changes to remote locking & tagging requirements.