Virtual Voltage Transformer for Substation Bus Bar Measurement
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Solution Overview
Problem
Conventional bus bar voltage determination in high and medium voltage substations is prone to electrical issues and single-point failures due to the reliance on physical voltage transformers and complex relay logic, which can lead to safety hazards and system instability.
Innovation Solution
A Substation Automation system using a virtual voltage transformer implemented as an Intelligent Electronic Device (IED) that determines bus bar voltage through network messages and switch status, eliminating the need for physical voltage transformers and reducing network traffic by utilizing a Virtual Local Area Network (VLAN) and standardized topology descriptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a physical voltage transformer (VT) is connected to a bus bar to provide instantaneous voltage values, then the bus bar voltage can be measured and distributed to all bays, but the VT becomes a single point of failure and requires costly maintenance that takes the switch yard out of operation
Solution Approach 1:
The patent creates a virtual copy of the voltage transformer function using software-based voltage transformation algorithms in the IED. Instead of relying on a physical VT, the system uses mathematical models to transform current measurements into equivalent voltage values, eliminating the single point of failure while maintaining the voltage measurement function.
Solution Approach 2:
The patent replaces the mechanical/electrical physical VT system with a digital/software-based voltage determination system. The IED uses computational algorithms to calculate bus bar voltage from current measurements and switch status data, substituting physical transformation equipment with electronic computation.
2Reliability
If relay or wiring logic is used to determine which bay VT is connected to the bus bar, then the system can identify the correct voltage source, but electrical problems and safety hazards arise if the logic fails or has time delays
Solution Approach 1:
The patent replaces electrical relay logic and wiring-based voltage source identification with digital communication protocols and software-based switch status monitoring. The IED receives digital status signals from switching devices and uses logical algorithms to determine connectivity, eliminating electrical contactors and relay-based selection logic that pose safety hazards.
Solution Approach 2:
The patent introduces a digital communication intermediary layer between the switching devices and the voltage determination logic. Instead of direct electrical connections and relay contacts, the system uses digital messages to convey switch status information, providing an safe intermediary that eliminates direct electrical hazard exposure.
3Ease of operation
If two VTs are accidentally connected to the central cable at the same time, then connectivity is established, but both VTs are destroyed causing danger to life and limbs
Solution Approach 1:
The patent replaces the physical central cable voltage distribution system with a digital communication-based voltage information distribution. The IED receives voltage information from multiple bays via digital protocols and selectively publishes the correct voltage value, eliminating the need for physical voltage connection switching that causes destructive short circuits.
Solution Approach 2:
The patent creates virtual copies of voltage information from multiple bays and distributes them through digital communication channels. Instead of physically connecting multiple VTs to a central cable (which causes destructive conflicts), the system digitally replicates voltage data and routes it appropriately, eliminating the physical conflict while maintaining information distribution.
4Measurement precision
If dedicated cables and A/D converters at all bays are used for voltage distribution, then accurate voltage measurement is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the IED multi-functional by combining current measurement, voltage transformation calculation, and voltage publication functions in a single device. Instead of requiring separate dedicated voltage measurement infrastructure (VTs, cables, A/D converters), the IED performs multiple functions using shared digital processing resources, reducing overall system complexity while maintaining measurement accuracy.
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention is concerned with Substation Automation (SA) system in high or medium voltage power networks, in particular for determining a bus bar voltage at a first node (1.3). The invention replaces a 'real' voltage transformer with an IED (8.1) or a 'virtual' VT, which determines the bus bar voltage at the first node from a first bay (7.4) connected to the first node. The IED receives network message from a second IED (8.3) of the SA system, indicating the bay voltage of the first bay connected to the first node. The IED also receives switch status of the switching device (2.9), arranged between the first bay and the first node, from a third IED (8.4). Depending upon the switch status, the IED establishes the bay voltage as the bus bar voltage at the first node.