Design And Implementation Of High Voltage Industrial Power System

A brown field industrial park is being planned for the Teesside area and the anticipated layout, in basic form, is shown in Figure 1 on page 3. Individual factories are numbered F1 to F19 and the anticipated load of each factory is given in Table 1.

The industrial estate 132/11kV substation will be supplied from a nearby 132kV overhead line by means of one underground cable terminated to one of the 132kV lattice towers via a compound. The fault level given by the DNO at the 132kV bus-bars is 2000MVA. The connections to the 132kV/11kV transformer are short single-core copper cables of negligible impedance.

The customers have all agreed with the landlord, in formal contracts, to provide financial support in order to ensure security of the 11kV electrical supply. With this agreement in place the main contractor is proposing to install three 11kV/400V transformers as the primary source of energy and these will be supplemented by local embedded generation, energy storage and static VAr compensation at your discretion. An option to provide islanded operation should also be considered, as this may provide opportunities in the future for a private industrial network.

It is intended to install a SCADA system to monitor and control the 11kV/400V network. It is your responsibility to recommend the items to be controlled and monitored by SCADA at each 11kV/400V substation, giving reasons for your recommendation and specify the SCADA functionality.  

Selection of Suitable Transformers and VAR Compensators

In the brownfield industrial Park, it is needed to provide electricity in the 400 volts range to the 19 factories as illustrated in table 1. The supply is to be taken from a nearby 132 kV power transmission line by means of a 132/11kV step-down transformer. The fault level in the bus bars of 132 kV line according to DNO is 200 MVA. Now, for the security of the 11kV line, furthermore, three 11 kV/400 V transformers are installed to provide 400 Volts supplies into individual factories. Additionally, an embedded generation with some energy storage device is needed to be installed to support the three transformers in case of power failure. A model of Islanded operation or load shedding operation is also needed to be installed to provide future development in the private industrial network. A SCADA system will be implemented controlling the whole 11kv/400 V network.

Table 1: Loads in Factories

The theoretical research for the entire project is segmented into mainly five parts. At first, suitable transformers are selected from a reputed manufacturer. Then for embedded generation of power in the 19 factories, a suitable static VAR compensator is selected accordingly. The next phase constitutes a proper plan of power generation when running in a load shedding mode or in Island mode, i.e. in case of power failure an emergency power generation system should be present to complete ongoing works in the factories to prevent loss of raw materials and effort. The whole system should be automated and controlled by some software and the using MATLAB for the programming of automation is the best option as it is a high-level language which will reduce the lines of code and efficient response can be obtained. The MATLAB code is then interfaced with some SCADA hardware for practical implementation of the entire plan.

In the brownfield industrial park, the substation will be supplied from a 132-kV overhead transmission line. Hence, a step-down transformer of 132/11kV will be installed in the substation. Winder Power is a reputed transformer manufacturer in the United Kingdom and provides transformer of different specification (Salodkar, Ghate & Kalwaghe, 2017). Hence, a 132/11kV step-down transformer of the specified ratings will be selected from the above transformer manufacturer company with the following specifications.

• Primary side voltage: 132 kV 3 phase delta
• Secondary side voltage: 11 kV 3 phase star
• MVA rating: 50 MVA
• Peak working ambient temperature: 40 °C
• Lowest working ambient temperature: -25 °C
• Ice loading: peak radial ice thickness is 12.5 mm.
• Earthing of the system: Based on the resistance and reactance of the supply line (Banerjee, 2015).
• System frequency: 50 Hz.
• Maximum system continuous voltage: 12 kV (rms)
• Minimum withstanding lightning impulse: 95 kV.
• Short circuit current at rated voltage for symmetrical fault: 21.9 Amps.
• Minimum air clearance: 400 mm for line to neutral and 430 mm for phase to phase.
• Safety clearances: 2600 mm from the closest unscreened live conductor and 2400 mm from closest point that is not at earth potential.

Now, from the primary transformer the supply voltage is stepped down to 400 V by three Step down transformers of 11kV/400 V transformers.

• Primary side voltage: 11 kV 3 phase delta
• Secondary side voltage: 400 V 3 phase star
• MVA rating: 3.15 MVA
• System frequency: 50 Hz.
• Peak working ambient temperature: 40 °C
• Lowest working ambient temperature: -25 °C
• Ice loading: peak radial ice thickness is 12.5 mm.
• Earthing of the system: Solid.
• High voltage tapping range: ±5%.
• Short circuit current at rated voltage for symmetrical fault: 10 Amps.
• Minimum clearance: phase to phase is 350 mm and phase to earth is 320 mm (Wang et al., 2017).
  

Implementation of Islanded Operation or Load Shedding Operation

As the entire system is a high voltage electricity generation system where 132 kV is stepped down 11 kV first and then 11kV to different low voltage side of 400 Volts power is distributed, hence, some static VAR compensator is needed to provide reactive power in an efficient way (Chandran, Sunderland & Basu, 2018). The function of the VAR compensator will be to bring the system very close to unity power factor (Eremia, Gole & Toma, 2016). The main two purposes of the VAR compensators are to regulate the 132-kV supply voltage within 5% of the limit and to improve the power qualities in the loads installed in the factories. Hence, the selected VAR compensator for the network is PCS-9580 static VAR compensation system.Features of PCS-9580 VAR compensator:

• Dynamic reactive source of power controlled by TCR, TSC, TSR and BSC
• System activity, stability and reactive power distribution can be optimized by RTDS and PSCAD along with the Analog Simulation Environment (Luo et al., 2015).
• Filtration of harmful harmonics to provide power in fundamental frequency and minimized dynamic loss of active power.

The real load value and the type of loads of the different factories inside the network are specified and hence from that information the KVA rating of the loads and the short circuit current rating of the loads can be calculated as given in table 2. The factories are assumed to be running in steady state loads (Mujawar et al., 2016).

Table 2: KVA calculation of different factories

Hence, the estimated total KVA rating of all the factories will be approximately 13981.969 KVA and the total short-circuit current rating will be 34.955 KA. Hence, if the three 11kV/ 400 transformers are to be designed as equally loaded then the capacity of each of the transformer must be at least 4660.656 KVA to meet the demand of the factory loads. It is also assumed that no factories will be running in the overloaded condition that is factories will not be using more than the load in KW as specified in Table 2.

One of the most important consideration is making the arrangement for Load shedding condition that can happen primarily in three levels.

This level is the most critical level as shutting down this level will cause power disruption in the entire network and in the factories (Gunawardana, Perera, & Moscrop, 2015). Hence, load shedding in this level is not recommended and if required then it must be done for very short interval and all the users of factories must be notified before the shutdown.

Load shedding in this level will cause shutdown in specific selected factories. This is much advantageous as this will not affect the production in all the factories and based on the requirement some factories can be shut down for maintenance of large time.

Integration of SCADA System

Load shedding in this level is the most efficient type of shutdown as this will only shutdown some sections in the factories. An example could be shutting down the warehousing system of the network while maintaining the lighting system in the factories. Integration of this type of shutdown require SCADA control in the network where load shedding can be performed remotely to specific sections of some selected factories. However, the software implementation can be costly and can be reduced to manual shutdown if required if agreed by the management of the factories.

This is a situation when the connection of the main transformer to the grid line of 132 kV is lost either by the planned or unplanned way. In this situation some sort of power generation inside the factories or in some place inside the park is required to meet the immediate power consumption of the factories is known as running in Island mode (Piyabongkarn, Buck & Dimino, 2016). Now, the maximum amount of power that can be required if all the factories are running in maximum load will be 13981.969 KVA and hence the power generation system need to be able to generate this amount of power. Now, it is expected that not all the factories are running at the maximum loaded condition at the same time and hence generation can be reduced accordingly. Employing load shedding in factory level or in 400 Volt network level, the amount of Island mode generation can also be reduced.Embedded generation options:

The power generation for Island mode can be done from several methods. Considering the worst-case scenario of generation of 13981.969 KVA at a time every method of generation must be present in the site. The different methods are given below.

A PV panel can produce approximately 1000 watts per square meter but the efficiency of the panel is only 20% i.e. only 200 watts can be extracted from one square meter (Das & Agarwal, 2015). The factories 1, 2 and 3 which are around 20000 m^2 each can produce a power of 4 MVA each and hence a total of 12 MVA can be produced. This meets over 90% of the total peak demand of power of 13.98 MVA.

Remaining amount of power can be generated by installing wind power turbine, gas turbine or diesel generator.

The SCADA representation of the entire network is given below. The green lines indicate the live sections of the network, where, the red line or components are either dead or sections with issues (Almas et al., 2014). The portions that are in the state of N/O (not working) are shown in red and those do not affect the network. The low voltage substation C is represented in red as it is open.

Options for Embedded Power Generation

Now, under faulty condition the green portions of the network become red as it happened in a fault that happened between substation A and B shown below.

Conclusion:

The total design of the project is presented in this paper with technical information and presentation. However, the detail calculations and the practical design of the Middleboro estate cannot be done due to the provided limited information. The information that is not provided in this context is distribution line properties like resistance, reactance and capacitance, the ambient conditions like humidity, temperature, electrical interference and more. The installation of multiple renewable energy generation systems entirely depends on the actual load demand in real time and the capital investment in the project. However, a must need to employ the SCADA system for controlling the remote load shedding, Island mode operation and efficient VAR compensation of the network.

References:

Power Transformers & Distribution Transformers | Winder Power. (2018). Retrieved from https://www.winderpower.co.uk/

Salodkar, M. R., Ghate, V. N., & Kalwaghe, S. S. (2017, November). Analysis of failure of a circuit breaker employed for capacitor switching: A review. In 2017 7th International Conference on Communication Systems and Network Technologies (CSNT) (pp. 109-112). IEEE.

Banerjee, R. (2015). Renewables in Microgrids Challenges and Opportunities.

Eremia, M., Gole, A., & Toma, L. (2016). Static VAr Compensator (SVC). Advanced Solutions in Power Systems: HVDC, FACTS, and Artificial Intelligence, 52, 271.

Das, M., & Agarwal, V. (2015). Novel high-performance stand-alone solar PV system with high-gain high-efficiency DC–DC converter power stages. IEEE Transactions on Industry Applications, 51(6), 4718-4728.

Chandran, C. V., Sunderland, K., & Basu, M. (2018). An analysis of harmonic heating in smart buildings and distribution network implications with increasing non-linear (domestic) load and embedded generation. Renewable Energy, 126, 524-536.

Piyabongkarn, D., Buck, E. F., & Dimino, S. A. (2016). U.S. Patent No. 9,472,954. Washington, DC: U.S. Patent and Trademark Office.

Luo, X., Wang, J., Dooner, M., & Clarke, J. (2015). Overview of current development in electrical energy storage technologies and the application potential in power system operation. Applied energy, 137, 511-536.

Almas, M. S., Vanfretti, L., Løvlund, S., & Gjerde, J. O. (2014, July). Open source SCADA implementation and PMU integration for power system monitoring and control applications. In PES General Meeting| Conference & Exposition, 2014 IEEE (pp. 1-5). IEEE.

Mujawar, S. T., Lad, S. S., Patil, M. R., & Mohite, P. U. (2016). THE POWER FACTOR CONTROLLER BY USING MICROCONTROLLER.

Gunawardana, S. M., Perera, S., & Moscrop, J. W. (2015). Transient Network Analysis of a 132kV Sub-transmission System Incorporating a Saturated Core Fault Current Limiter. In International Conference on Power Systems Transients (IPST).

Wang, W., Han, Y., Yu, H., Zhang, N., & Yan, L. (2017, May). Incorrect operation accident's analysis in overvoltage and differential protection of main transformer clearance. In Data Driven Control and Learning Systems (DDCLS), 2017 6th (pp. 584-586). IEEE.