Supervisory control and data acquisition (SCADA) is a critical tool used by utilities to remotely monitor and control their distribution operations. Indian utilities are equipping their substations, distribution transformers and feeders with remote data transmission sensors and instruments as part of SCADA implementation. These devices collect information about the power flow and other system parameters and transmit it to a central server for monitoring. This information can be used for critical load flow studies and system planning.
Some of the key components of SCADA are remote terminal units (RTUs), multifunctional transducer (MFTs), local data monitoring systems (LDMSs), heavy duty relays (HDRs), contact multiplying relays (CMRs), auxiliary power supply systems, UPSs and direct current (DC) power systems.
RTUs are microprocessor-based electronic devices that provide an interface between the SCADA control centre and the field equipment. They acquire data from the MFT and transmit it to the control centre. The RTU receives and processes digital commands including breaker on/off and relay reset signals. The RTU can also double up as a data concentrator with IEC60870-5-101/104/MODBUS protocols.
MFT inputs are taken from the metering equipment or transformers following which analog signals are processed and sent to the master control unit. MFT collects the data and calculates the phase-to-neutral voltage, phase-to-phase voltage, three-phase current, active power, reactive power, apparent power, power factor and frequency, etc.
The LDMS is a human machine interface (HMI) that presents the processed data to the substation operator. The HMI is typically linked to the SCADA system’s databases and software programmes to provide the trends and management information, and diagnostic data.
The CMR is used for indicating the on/off status of circuit breakers, close/open status of isolators, charge/discharge status of springs, etc. Meanwhile, the HDR is operated from the RTU/ control centre to draw high current for the operation of certain equipment.
The fault passage indicator (FPI) is a device that provides visual information on any fault in the power system. In SCADA, the FPI is integrated with the control centre through pole-mounted RTUs so that the real-time status of equipment like distribution lines is available at the control centre. Meanwhile, the ring main unit (RMU) acts as a mini substation for a 33 kV or 11 kV line to isolate the faulty section of the line and restore the balance section by extending supply from other feeders.
Madhya Pradesh Paschim Kshetra Vidyut Vitaran Company Limited (MPPKVVCL) has made significant progress in SCADA deployment. The discom is implementing SCADA in two towns – Indore and Ujjain. The project entails the integration of 72 33/11 kV substations in Indore and 20 33/11 kV substations in Ujjain with their respective control centres.
So far, control centres have been operationalised and RTUs and LDMSs have been commissioned across the specified number of substations in both the cities. In addition, five RMUs have been installed in Indore and feeder RTU integration has been tested. Further, two FPIs have been installed in Indore city and the integration of FPI with the SCADA system has been completed.
The SCADA control room has been functioning in Indore for over two years now and is being operated in three shifts on a 24×7 basis. Indore’s distribution network has five divisions, and accordingly its SCADA control centre has been divided into five sections with a supervisor for each. All 72 33/11 kV substations have been integrated with the SCADA control room and they are being monitored and controlled on a 24×7 basis.
MPPKVVCL has accrued several benefits from SCADA implemention. SCADA has enabled real-time monitoring of all the 33/11 kV substations in Indore. Parameters such as DC voltage, load current of feeders and transformers, substation power supply status, breaker status, and spring charge status of substations can be easily monitored by the utility. All substation operations including breaker functions and relay resets are now being carried out from the SCADA control centre.
SCADA helps in the early detection of problems and therefore resolves the issue before equipment failure. It has also helped the utility to identify the feeders with greater number of faults through the generation of daily feeder outage and tripping reports. This results in better maintenance and increases the number of hours of electricity supply.
Further, all vacuum circuit breakers installed in the electrical network flash an alarm after a pre-defined number of operations so that timely maintenance can be carried out. This enables preventive maintenance of the breakers and enhances the life of the equipment in the electrical network.
With the help of system applications, reactive power can be controlled at the substation for better quality of electricity in terms of voltage and power factor. Also, load shedding activities with load prioritisation can be planned and conducted.
In addition, from the relay data, the utility can analyse the faults in feeders and reduce trippings. Also, SCADA operators can determine the nature of the fault and take corrective action to rectify it. This helps in increasing the life of power transformers and other critical equipment in substations. Notably, no power transformer failure was recorded after SCADA operationalisation in Indore.
In addition, the utility acquires telemetry data from substations to analyse augmentation needs and undertake load forecasting. Various alarms are configured in the SCADA system for better monitoring of transformers, 33 kV feeders and 11 kV feeders, which helps prevent outages. Further, energy reports for all the substations are being generated for review by the management.
Challenges and the way forward
Although MPPKVVCL has benefited immensely from SCADA, the road to its implementation was not devoid of challenges. SCADA is being implemented in two parts of the R-APDRP (A and B) and since the scope of work of both parts is different, separate agencies have been selected for the two. Also, though work under SCADA Part A was completed about two years ago, the installation of RMUs and feeder RTUs is still left, as a result of which the complete benefits of SCADA have not been realised so far. Around 311 RMUs have to be installed in Indore and 114 RMUs in Ujjain. The targeted date for completion of SCADA- related works is March 2018. Overall, MPPKVVCL’s objective for SCADA implementation has been to reduce the fault clearance time with the help of RMUs and FPIs, thereby improving the supply hours of feeders resulting in better System Average Interruption Frequency Index and System Average Interruption Duration Index.
Based on a presentation by Achal Jain, Superintending Engineer (R-APDRP and SCADA), MPPKVVCL, at a recent Power Line conference