Problemas de calidad de energía en India

Las empresas de distribución de energía de la India, Discoms, son responsables del suministro y distribución de energía a una variedad de consumidores (industriales, comerciales, agrícolas, domésticos, etc.). Este es también, según el Instituto Brooking, el eslabón más débil del ecosistema energético desde una perspectiva de sostenibilidad tanto financiera como operativa.

La calidad de la calidad de la energía.

Por supuesto, el suministro de energía no es sólo una cuestión de conectar los hogares a los cables y recaudar ingresos por los servicios prestados. Requiere el suministro de energía de buena calidad y constante a esos consumidores. Esto es especialmente cierto para las empresas industriales y comerciales que operan dentro del área de servicio de Discom.

Los picos de voltaje, los armónicos o las interrupciones, independientemente de su duración, pueden dañar el equipo y lo dañarán. Además de los daños a los equipos sensibles y las costosas reparaciones posteriores, los problemas de calidad de la energía provocan pérdida de tiempo, datos corruptos, menor productividad y reducen la esperanza de vida del equipo.

La Iniciativa Asiática de Calidad de la Energía destaca la importancia del monitoreo continuo de la calidad de la energía (PQ), un alejamiento del enfoque "reaccionario" más tradicional adoptado anteriormente.

Afirman que “el monitoreo continuo de la PQ es probablemente la única forma de monitorear y analizar con precisión los problemas que surgen debido a una PQ deficiente”.

Los beneficios resultantes incluyen:

Gestión proactiva:  Permite identificar tendencias y extrapolar los riesgos a la seguridad y fiabilidad en puntos concretos de la red eléctrica.

Ayuda al mantenimiento preventivo y predictivo:  la información sobre cómo reacciona el equipo ante eventos o perturbaciones de PQ específicos proporciona la previsión para tomar acciones correctivas oportunas. También permite a los equipos de mantenimiento optimizar la ventana de mantenimiento preventivo proporcionando información que antes no estaba disponible. Se pueden diseñar procedimientos específicos para evitar interrupciones y prevenir fallas en base a los datos del monitoreo continuo.

Con capacidades de diagnóstico para condiciones específicas, el monitoreo de PQ puede crear un impacto significativo en el desarrollo de programas de mantenimiento preventivo. Detección temprana de problemas: los parámetros PQ especificados en la red permiten al sistema identificar y enviar alertas cuando las condiciones comienzan a deteriorarse. Esto garantiza la solución oportuna de los problemas de PQ antes de que puedan causar daños.

Planificación precisa de la inversión de capital para mejorar la PQ: una consideración importante es la capacidad de planificar con precisión futuras inversiones de capital debido a la disponibilidad de datos históricos y en tiempo real. El monitoreo continuo de la calidad de la energía brinda acceso a esta información detallada.

Garantizar el cumplimiento: la lista de verificación regulatoria y de cumplimiento para los parámetros de PQ se expande continuamente. PQ es una parte integral de varios programas internos de control de calidad, normas específicas de la industria y estándares internacionales.

Formato de intercambio de datos de calidad de energía

One of the key goals of PQ monitoring is to be able to establish a benchmark for PQ, whether it’s across a facility or at an industry level. Continuous PQ monitoring is becoming increasingly adopted across the sector, accompanied by a rise in the diversity of PQ software applications, underlying database platforms, and logics to run simulations and analyse data.

A Power Quality Data Interchange Platform (PQDIF) specifies a common format for PQ measurement. The IEEE Power Engineering Society Task Force is standardising the data interchange format. The guidance provided by the neutral platform is key to ensuring a consistent form of data exchange between software and monitoring devices for its universal applicability.

Consumer-centric service contracts

SAIFI, SAIDI, MAIFI – while all are used to measure distribution system reliability, they may not be detailed enough to provide information about the reliability for two utilities with different feeders. Nor do they necessarily take into account the proportion of interruptions caused due to faults at the customer end.

Continuous PQ monitoring systems, however, provide more accurate insights which can be easily tracked and analysed to improve performance and get flexible contracts that reward customers maintaining good PQ.

Poor PQ is one of the root causes of business problems including productivity losses, downtime, loss of reputation and goodwill, customer dissatisfaction and much more.

Continuous Power Quality monitoring provides an opportunity to gain real-time insight into the health of a power system and is a vital and integrated part of the power system to maintain its reliability.

Smart Energy International spoke with Chintamani Chitnis, Head: Grid Operations, Power System Control Centre (PSCC) in Mumbai, about specific challenges being experienced within the state of Maharashtra concerning power quality.

Power Quality is an issue that has been taken very seriously by the transmission and distribution system operators in the state.

The distribution level network is almost 95% underground and is therefore little affected by extreme weather events. However, the transmission system is affected, and for this reason, automation of the system has been undertaken – through SCADA on the transmission side, and a distribution management system (DMS) on the distribution side – in order to minimise the impact on customers.

All operations at 220kV level are 100% automated, and all transmission networks are N -1 compliant, meaning that redundancy to the level of 100% is achieved in terms of consumers.

The subsequent System Average Interruption Frequency Index (SAIFI), System Average Interruption Duration Index (SAIDI) and Consumer Average Interruption Frequency Index (CAIFI) scores are the best in India and are comparable with the best in the world, says Chitnis. This is primarily due to the network planning being done in such a way as to enable continued connection to customers even if a feeder should be lost. Even if a feeder should be taken off the grid, there is always another feeder available.

Related in the distribution network the underground network automation systems are handled in such a way that the network is fully equipped with fault passage indicators and the ring main units are fully automated; thus many distribution substations have an auto-transfer scheme and manual intervention is totally avoided. Self-healing grid functionality is wholly decentralised, and there is no manual intervention at all from central control.

End-consumer interruptions thus sit at about 20 minutes a year. By utilising an ‘islanding system’, power supply in Mumbai is assured uninterrupted within the city limits. Disruptions to the grid in the Western Regional Power grid results in automatic isolation of the city from the rest of the grid.

The total customer base in Mumbai is about 3.5 million, with Chitnis’s team being responsible for 750,000 customers. The total consumer base is divided between four different utilities in Mumbai and consumers have the option to switch ‘wires’ to another utility as they wish.

“Unlike in other parts of the world where this likely happens only on the supply side, in Mumbai you can change even the wires,” says Chitnis.

“Therefore the continuity of supply you afford to the consumers is of paramount importance for each of the utilities. As a result, consumers switch for multiple reasons, including tariff or power quality.”

Automation on the transmission and distribution networks.

The distribution networks in the area are automated up to about 40% for big substations. Substations are automated in a ring configuration connecting two substations and smaller substations in-between.

“If there are ten substations in a ring, 50% of them will be automated. The philosophy of automation is provided in the first leg of the ring and somewhere in the middle – more commonly known as the mid-way operating point. In the case of a fault on either of the sides, you can switch the consumers to an alternate feeder. This is done with the help of fault passage indicators which are communicable and visible on the DMS. If an operator notices any tripping on the DMS, he automatically also sees what kind of fault passage indications are available on each of the stations and, based on the fault passage indicators, he isolates the section indicated and inferred to be faulty, and restores it.

The total restoration time we usually have in terms of automated substations is less than 2-3 minutes for each of these rings.

“At some critical consumer locations, we have an autochanger scheme where the operator doesn’t have to intervene, and there is an automatic change over to another supply in the event of the normal supply tripping, without any manual intervention. So within a matter of milliseconds this changeover happens.

“The communication is enabled through GPRS and fibre for the bigger substations. All of these assets are mapped on our GIS, and therefore in real-time we can see what areas are out of supply and restore the consumers who are affected.

The GIS is connected to the CRM, and this allows customer service representatives the opportunity to identify and provide accurate information on restoration efforts when they are speaking to customers who have called in regarding an outage.

On the transmission lines, the high rated substations are primarily gas-insulated substations and are 100% automated.

In addition to operations, transformers and voltage correction can be controlled remotely in cases where voltages fluctuations are experienced. There are various other alarms built in, where for instance, voltage variations are clearly highlighted. Overhead lines are equipped with auto reclosers which, in the event of a transient fault, will island the feeder and enable restoration of the line within a matter of milliseconds.

Cascading blackouts have been almost completely eliminated, but as a backup, load trimming is possible to reduce the load on a specific line and ensures the line remains active. This infrastructure means system load is controllable to avoid blackouts.

Cyber protection

Disaster management plans are in place and the responsibility of the IT department.

However, IT and OT systems are kept entirely separate from one another, and it is through this that threats to the external network are minimised. Additional security features include compliance with international cybersecurity standards.

The fibre networks operate on a similar ring system to the topology, by the transmission and distribution networks.

And while the cellular networks do suffer command failures from time to time, the percentage of these are around 5% and considered fairly minimal. 95% – 97% is the norm in terms of communication availability across the network.

Longer-term outages which cannot be addressed by rerouting the supply, and which are caused by accidents on the physical grid, are dealt with swiftly.

Standard procedure is to provide portable generation to the affected areas, thereby restoring power supply. In most cases, supply is fixed and restored within a period of three hours. These kinds of incidents are rare, occurring perhaps once or twice per annum.

Sin embargo, lo que más preocupa a las empresas de servicios públicos de Mumbai es la calidad de la energía en la red. Los aumentos repentinos o las caídas en el suministro se deben principalmente a la naturaleza interconectada de la red y las perturbaciones en la red se trasladan al nivel de los consumidores (normalmente grandes empresas industriales o comerciales) y se manifiestan como caídas de tensión. Estas caídas transitorias pueden afectar la maquinaria local y generar costos de reparación significativos para el consumidor.

Las consideraciones sobre la calidad de la energía se controlan desde dos lados. Por un lado, en el lado de carga y, por el otro, a la altura de la rejilla.

El porcentaje de caídas vistas por los consumidores es directamente proporcional al nivel de falla del sistema.

“Como operador del sistema, y ​​en consulta con otras empresas de transmisión y el centro estatal de carga y despacho, estamos tratando de migrar de una filosofía de operación continua a una filosofía de operación seccional. Al seccionar las operaciones, se prevé que los niveles de fallas disminuirán drásticamente.

“Lo que hemos podido hacer es reducir la magnitud de las caídas de voltaje y, por lo tanto, las caídas de voltaje que antes eran del 75% o del 100% ahora se reducirán drásticamente a entre el 0% y el 25%. Esto significa que si el voltaje es 100 kv, ahora verá una caída de hasta 75 kv en comparación con las caídas anteriores a 25 kv”.

Al seccionar los buses EHV y reducir los niveles de falla en aproximadamente un 50%, la magnitud de las caídas de voltaje se ha reducido drásticamente y, por lo tanto, el consumidor es casi inmune a las caídas de voltaje.

Debido a que la duración de la caída de voltaje también es importante y principalmente una función de los sistemas de protección que no funcionan correctamente, cualquier disparo al nivel de 220 kV debe desaparecer en 160 milisegundos.

Lo que se ha hecho para abordar este requisito específico es la instalación de sistemas de protección que tengan todos relés numéricos y sean capaces de eliminar la falla en 160-200 milisegundos y al mismo tiempo limitar la caída de voltaje a aproximadamente el 20%. Todos los equipos de la línea son capaces de sostener esta caída de magnitud y duración.

Chitnis concluye: “Así es como hemos podido mitigar el riesgo. Comenzamos este programa el año pasado y podemos ver que los consumidores no se ven afectados durante aproximadamente el 75% de las caídas de voltaje normales que ocurren en el sistema”.