The increased amount of substations remotely controlled from control centers has caused great concern regarding the responsiveness of operators, especially in cases of major events such as partial or total blackouts in the electric power system.
In these situations, operators should perform a very high amount of commands, first in preparation for the power system restoration (disconnections) and subsequently for the fluent restoration (not coordinated by the ISO) itself. These procedures should be performed for each of the plants that were shut down in the blackout. There is also a phase coordinated by the ISO, when operators must await instructions for the continuation of the process.
In order to reduce the time of the fluent phase of restoration it was elaborated in the Supervision Engineering sector of CEEE-GT (utility from the south of Brazil), a project that aims to gradually add automation and tools to assist operators to complete their tasks more efficiently and accurately.
The project was divided into stages to facilitate the implementation and enable operators through training and practice, accustom and gain confidence in the automatisms. The steps are:
- Semiautomatic process (initiated by the operator) to prepare for the restoration.
- Fluent restoration support screens for each substation.
- Availability of Operating Instructions (OI’s) directly in the IHM’s (PDF docs).
- Automatic process for preparing the restoration .
- Semi-automatic process for execution of the fluent restoration .
- Automatic process execution fluent restoration.
We are currently implementing Phase 1. The HMI platform used in remote centers is the Open Substation HMI (OSHMI, http://oshmiopensubstationhmi.sourceforge.net) which is open source software. The automatic controls are implemented in the LUA language (https://www.lua.org), a computer language designed to extend applications that was embedded in the HMI for creating scripts.
The scripts were divided into one for each substation to facilitate maintenance. Each script executes a check of the blackout occurrence conditions around the substation:
- the validity of the measurements is checked;
- the absence of voltage is observed in the buses;
- the absence of flow at transmission lines terminals.
To predispose the automatism preparation is also checked whether any bay is transferred, which may indicate an anomaly situation in the facility.
When the automatism is predisposed, for the operator is presented a “START” button on the single line HMI screen and also on the screen dedicated to the restoration. Upon command of the operator starts the automatic shutdown process of the substation circuit breakers (in some cases more than 50). This automation can be triggered simultaneously for several substations.
The execution of the commands has become much faster than previously when the operator was obliged to consult the OI’s on paper, check the conditions, the command sequences and find on the screen the objects to be controlled. It is now also a much more secure process, as it is harder to miss the sequence, the conditions and the objects to be controlled.
The operator training is done by the simulation of occurrences and the execution of the preparation and restoration processes.
This is another among other projects where we try to focus on the users (User Centered Design) and their respective tasks, applying the High Performance HMI concepts (cognitive theories) to improve the Situational Awareness and consequently the performance of the operators.
Ricardo Olsen , MEng. :: CEEE-GT