Analyze Better to Operate Best
Introduction
Primary objective of incorporating PRDC® was to provide consulting services to the power utilities and industries. Power System Consulting remains to be the core business of PRDC®. The consulting group has grown by leaps and bounds, and is known to be one of the largest of its class today. PRDC® is proud to have a strong team of highly qualified technocrats supported by seasoned panel of consultants with rich experience of over 40+ years in the industry.
Services encompass a wide spectrum of power system studies ranging from analysis of a nanosecond time frame phenomenon to forecasts for several years ahead. The clients include small industry to expansive national grid spanning thousands of nodes spread across several million square kilometers. The projects span from basic loss calculations to complex network proposition and market mechanism.
With diverse client base spread across India, PRDC® also covers international clients across many continents. The group handles hundreds of projects at a time in major sectors like state owned and private generation, transmission and distribution companies, industries like steel plants, aluminum plants, cement industries, petro-chemical industries etc. Most of the projects are carried out using indigenously developed power system analysis and simulation software – MiPower®. It is the flagship software product of PRDC® that is extensively used by thousands of users across the globe. Other standard software products are also used depending on the client’s preference.
Consultancy services include both utility or grid connected and industrial or commercial businesses. Consultancy services are offered in various simulation time frames from nanosecond / micro-second time frame for very-fast-front transients, fast-front transients, millisecond for slow-front transients, ferro-resonance simulation and seconds to minute time frame for transient stability, dynamic stability, sub-synchronous resonance and steady state operation conditions like load flow analysis, short circuit analysis, protection co-ordination, harmonic analysis and voltage stability.
World is moving towards sustainable energy. Solar and wind are two major renewable energy sources that is widely being adopted globally. PRDC® offers its services to the investors, developers, utility and regulatory authorities. Services include pre-feasibility, detailed technical feasibility of grid integration, development of grid code, strengthening of existing grid code, assess grid code compliance etc. PRDC® has done almost all the wind energy studies in India, Indonesia and Mongolia. Most of the solar energy studies in India and Fiji are also done by PRDC®. It is an honor to proudly proclaim that Wind Energy Grid Code of India is prepared by PRDC® and amendments were done to Indonesian grid code. PRDC® is also working on grid code for facilitating cross-country power flow in South Asian region.
PRDC® has developed models and offers consultancy services in demand forecasting (time series, econometric and partial end use modeling), reliability analysis, load research, cost to serve, business plan for utilities, energy auditing & accounting, ground / earth mat design, insulation co-ordination, design of NGRs and disturbance analysis etc. Having expert teams with research capabilities and cross functional experience in the power sector, PRDC® can undertake all types of power system simulations and offer effective and quality solutions to all the customers.
PRDC® does turnkey works involving detailed engineering, pre-feasibility, detailed technical feasibility, DPR (Detailed Project Report), DTS (Detailed Technical Specification) with BOQ, RFP preparation, vendor identification, tendering assistance, vendor evaluation, procurement management, project management, monitoring, quality assurance, verification and certification services. Owner’s engineering consulting and project management consulting are also offered.
DEMAND FORECAST
The load forecast for the utilities/other clientele would cover long term, medium term and short term forecasts for the periods of up to 25 years. Long term and medium load forecasts are more concern to utility planners and short term load forecasting is more concern for system operators. The modelling considers the historical data along with other relevant data which includes weather parameters and socio-economic information. Based on the available information and requirement of the client, we develop the forecasting models by various techniques like time series, econometric and partial end use, regression models, etc for Long term load forecasting. Forecasting models would be validated by curve fitting techniques to compare with historical data and it will be forecasted for future years by creating various scenarios.
The forecast model would also consider the data gaps and inconsistency in the information and provide a stable model. The best suited load forecasted values are essential for utility at state level to plan for generation transmission resources. We also provide service for load forecast for cities where precise load forecasting at sub zone or group wise is required to plan for future substation level demands. This will be performed considering spatial load forecasting technique to find where, when and how much load growth is expected for future years. The functional diagram of long term and short term load forecast are presented below.
GENERATION PLANNING
With the growing demand and reduced conventional resources coupled with increased attention to greenhouse gas impact, generation planning has gained momentum in the utility studies. At PRDC®, the assessment is performed using reliability analysis considering the reliability levels (LOLP or LOLE) as described by grid codes using probabilistic approach. The studies will assist in generation expansion planning and production costing.
This assessment also helps to plan the maintenance scheduling of conventional units with same reliability level in all the months/seasons. The studies will help to plan for energy limited units like hydro or gas based units for peak load hours. The studies will also address the plant life management which helps the utility when and what type of plants to be planned or upgraded considering the existing plant life times. The planning will also considers the emission constraints while providing the decision on future alternatives generation plans.
For renewable integrated power systems, the assessment is to understand the impact of renewable power generation towards meeting system peak demand, in other words the renewable capacity credit towards improving system reliability. Generation planning studies provides the utility planners to find the surplus/deficit peak powers and energy requirements for better planning of exports and imports respectively. At grid level, planning study will help to plan integration two or more state grid and advantages for all interconnected systems.
This will help utilities to plan flexible energy sources across the region and to maximize the renewable energy penetration. At the end the utility can plan the best economical alternative generation mix scheme for future years. The generation planning is also integrated with the transmission system to assess the adequacy of transmission system which also provides framework for assessment of transportation problem. The functional diagram of Integrated resource planning is presented below.
TRANSMISSION PLANNING
Transmission planning studies covers planning of new substations, transmission lines, reactive power support in terms of capacitors and reactors, dynamic compensations, augmentations to existing substations, etc. to cater the demand growth. Transmission planning studies would be of utmost importance to all the electricity transmission companies around the world. All the transmission utilities have to plan their infrastructure requirement in the short term, medium term and long term due to load growth, new generation additions, seasonal variation of load and generation, reliability requirement etc…
Generally transmission planning includes studies like load flow, contingency analysis, short circuit and transient stability. Also load forecasting, generation planning, voltage instability, switching-overvoltage, insulation coordination can be part of the assignment based on the requirements of the utility. Transmission planning examines peak load, light load, high hydro, high thermal and various other scenarios to optimize the infrastructure requirement. Reliability of the transmission network would be analyzed by performing contingency studies. Planning would be carried out by considering the applicable grid codes and regulations. Overall investment required for the transmission infrastructure would be included upon request to assist the utilities in planning their budgets.
DISTRIBUTION PLANNING
We undertake distribution planning assignments for implementation of distribution development schemes in a large scale. Substation wise load growth is essential for planning distribution substations. We analyse the existing infrastructure and network capacity to plan the additional infrastructure required for the implementation of proposed scheme or strengthen the existing system. This helps DISCOMs to plan for additional transformers and distribution lines to strengthen the system. The activity also covers the estimation of investment (Capacity Expansion, CAPEX) required for proposed infrastructure and technical feasibility and economic viability of the investment.
We provide the solutions to minimize the losses in the system with alternative paths for power flow by performing load flow studies at distribution voltage levels. We have carried out many simulations for APDRP and R-APDRP works for most of the states in India also recent study of Gram Jyothi feeder segregation program in specific to Karnataka. The also provide the service to find the distribution reliability indices to find the quality of the supply at customer end and DISCOMs. This will help DISCOMs to plan better and find alternative ways to provide high reliable power to customer at best economical way.
CONVENTIONAL GENERATION
Power evacuation and grid connectivity services cover design and analysis of evacuation schemes/alternatives for the generation projects considering relevant standards and grid codes. Based on the location and capacity of the generation plant, various schemes/alternatives would be analyzed to suggest the technically feasible grid connectivity scheme. With the extensive database of power system network available in PRDC®, the detailed model of system under study would be built for load flow, contingency analysis, short circuit and transient stability analysis. Based on several simulations spanning various operating conditions, performance of each of the considered options would be evaluated to understand the technical feasibility of each alternative. The cost analysis would also part of the analysis in determining the optimal and technically feasible options. The studies would also determine the reactive compensation requirement and insulation co-ordination.
Grid connectivity studies have been carried out for many private and state owned generating companies for checking the corridor availability to transfer power in both intra state and interstate transmission system. PRDC® also offers grid connectivity studies to check the feasibility of supplying power to their own consumers situated in different locations considering different options along with the comparison of open access rates considering both present and future network so that suitable decision can be made and feasible option can be discussed/finalized with utility for sending power to their consumer end.
RENEWABLE GENERATION
Wind and solar generation both experience intermittency, a combination of non-controllable variability and partial unpredictability and depend on resources that is location dependent. Hence grid connectivity and evacuation studies for renewable generations are necessary to assess the capability and reliability of the grid to evacuate the power from the wind or solar plants. Planning, operation and control of RE integrated power systems poses a variety of challenging problems such as the ability of the network to accommodate these generation, Voltage rise/drop, effect of these generations on fault levels etc. The solution of which requires extensive analysis of power systems integrated with renewable generations. Analysis comprises of load flow, contingency, short circuit, transient/dynamic stability analysis and also reliability analysis of the transmission system along with the proposed renewable generation. These analysis would be carried out considering relevant standards and grid codes. Optimization of internal wind farm network along with due-diligence of the proposed system is another area offered from us.
As an end to end solution, we also offer the micro-siting arrangement of individual wind turbines, internal wind farm design, engineering and project management of sub-station, transmission system and Balance of Plant. Our report provides clarity on power evacuation aspects to both investors and developers for taking suitable decision and is bankable document for the investment. We study the technical feasibility of wind/solar sites considering different evacuation schemes and our report acts as a support document for developers while approaching utility for the grid connectivity.
CONVENTIONAL SYSTEMS
To operate the system effectively with various stakeholders, it is essential to have procedures for planning, connection of various equipment’s in the grid and operation of the grid which will facilitate secure and optimum power system operation. Grid codes are the rules laid by the authorities for all its stakeholders, i.e., the users and power generating stations for connecting to the network and operate as per the standards. The grid codes mandates regulations and standard to be followed for connecting important power system components like new generators, transmission lines, protection system etc.
Based on the grid code regulation, we at PRDC® provide detailed studies and analysis to check the connected components whether they are grid compliant or not. We also provide assistance for making/changing grid codes in planning, connection, operation, protection, metering, scheduling dispatch and marketing guidelines. We have provided the services like making grid code for various countries like India, Indonesia, Fiji and also for grid code for cross border trading between countries or between regions.
RENEWABLE ENERGY
To operate the system effectively, a large number of components, such as protection systems, monitoring systems, operational procedures, etc. are required to work in a synchronized and efficient manner; otherwise, contingencies may arise in the system. Recent trend of penetration of the renewable energy sources to the grid has further enhanced the complexity of the network. Due to their stochastic nature, their integration has added more uncertainty to the grid, leading to increased concerns related to the accurate prediction of generation and control of power flow. In addition, the deregulation (privatisation and liberalisation) in the electricity sector have invited more generation and supplier entities to meet up the ever-growing demand of electricity. This addition of the new generation schemes along with a large number of competitors has led to following new challenges for the proper planning and operation of the present and future power systems: Increased level of complexity, Stochastic nature of power transfer capabilities and Bidirectional power flow across the system.
To safeguard, the electric power systems, against failures and address the issues raised, rules and regulations are required. These rules act as standard procedures and requirements for including or prohibiting connection of the generation plants and loads to the grid. The rules should be applicable to the both, new and existing, generation plants and users, who are interested to connect to the grid. Grid codes are attempts in this direction to ensure supply quality for the consumers. PRDC® has provided services to make grid codes for renewable energy sources which helped the utilities by providing grid integration procedures for connectivity and operation to accommodate the renewable in grid.
Industrial Power System
The planning, design, and operation of industrial and commercial power systems require several studies to assist in the evaluation of the initial and future system performance, system reliability, safety, and the ability to grow with production and/or operating requirements. Typical studies required are load flow studies; short-circuit studies, protection coordination & arc flash studies, transient stability studies, grid islanding & load shedding studies, harmonic studies, motor starting studies and switching transient’s studies. At PRDC® , we have carried out power system studies for various steel plants, cement plants, aluminum & ferro alloy plants, process engineering plants etc. both in India and abroad.
PROTECTION CO-ORDINATION
We have the expertise in protection coordination and simulation for industries and utilities. We have modeled an entire electrical system of few countries right from Generation plant to Distribution transformer level for the protection simulation and fine tuning the co-ordination. Our expert engineers visit the site and collect all the relevant data required for protection coordination to suggest the optimal relay settings for over current, distance protection, unit protection etc…
Complete electrical network is modeled in the software tool to carry out the relay coordination. We undertake grid islanding and load shedding studies for islanding of captive generating units in case of grid disturbances and stable operation of captive generation with matching load subsequent to islanding for industrial power systems.
PROTECTION SIMULATION & ANALYSIS
This type of analysis can be utilized to verify various types of protective schemes employed in the system. Verification operations for performance of CT, CVT, relays and other protective equipment’s would be carried out based on the disturbance records. The performance of protective scheme shall be assessed under various critical situations such as faults, load throw off, higher loading on system, relay mal operation etc.
Previous fault waveforms will be used to analyze system behavior with current settings or any other fault may be simulated to test the settings. Relay settings shall be checked for prompt operation as well as proper order of operation, from primary to backup for various faults.
PROTECTION AUDIT
The protection system should perform flawlessly to ensure that there is no reflection of major disturbances in one area to the entire network. These issues are best tackled by going in for protection audit and review at regular intervals. We undertake protection audit for the industrial units, utility substations and transmission systems.
Our experts visit the site for carrying out the protection audit and task revolves around inspection of the substation and its vicinity along with the understanding of the complete network.
The details of existing protection schemes and relays, their settings, earthing systems, details of equipment’s (both main and auxiliary equipment’s) along with their ratings shall be collected for detailed analysis. In order to understand whether protection system is functioning adequately or not, the recent tripping incidents shall also be analyzed. The protection audit would also evaluate the system compliances as per the applicable guidelines and standards.
INSULATION CO-ORDINATION
Insulation co-ordination study is the process of establishing the required basic insulation level (BIL) of various substation equipment and for determining the ratings, placement and adequacy of surge protective system. This includes simulation of temporary overvoltage, slow-front transients, fast-front transients, very-fast-front transients etc…
Those are simulated using MiPower® and PSCAD software. In a nutshell, the basic goal of the study is to analyse various kinds of possible overvoltage transients in the system and provide optimum mitigation techniques to prevent failures in substation equipment under electro-magnetic transient conditions.
Phase-A voltages at different locations in substation during direct lighting stroke to overhead transmission line.
EMTP STUDIES
In addition to insulation co-ordination study, Electro-magnetic transient studies are also carried out for providing solutions on array of different applications and requirements. Amongst these, selection of circuit breaker by analysing the transient recovery voltage (TRV), rate of rise of recovery voltage (RRRV) and interruption capability of circuit breakers during switching operation of power system elements, overvoltage and induced voltage analysis to assess the transient voltages accruing with switching operations of the transmission systems, capacitive and reactive loads and dynamic-
overvoltage’s due to load rejection, fault condition etc., analysis of secondary arc current during single phase to ground fault and determination of rating of neutral grounding reactors for successful auto-reclose operation, analysis of arcing ground faults and mitigation techniques, analysis of failures of electrical equipment like circuit breaker, transformers etc. under transient operational conditions, study of possibilities of ferro-resonance in electrical system and mitigation solutions etc. are some of the areas addressed under electro-magnetic transient studies.
Phase-A voltage during shunt capacitor bank switching (peak bus voltage -1.88 p.u)
Phase-A voltage at receiving end bus during line energization
HARMONIC MEASUREMENTS
Harmonic measurements are carried out on industrial or commercial sites: to obtain an overall idea on distribution-network status, to determine the origin of a disturbance and determine the solutions required to eliminate it, to check the validity of a solution. The harmonic indicators can be measured by an expert present on the site for duration of from 1 hour to 1 week based on the type of measurements or in some cases the meters will be connected permanently installed in the distribution network, allowing a follow-up of Power Quality.
The results of measurement will help the analysis in order to: to determine any necessary de-rating of equipment in the installation or quantify any necessary harmonic protection and filtering systems to be installed in the distribution network or to check the compliance of the electrical installation with the applicable standards or Utility regulations (like IEEE and IEC standards).
Measurement devices provide instantaneous and average information concerning harmonics. Instantaneous values are used for analysis of disturbances linked to harmonics. Average values are used for Power Quality assessment. The results will be provided for: harmonic spectrum of currents and voltages (amplitudes and percentage of the fundamental), THD (Total Harmonic Distortion) for current and voltage, for specific analysis: the phase angle between harmonic voltage and current of the same order and the phase of the harmonics with respect to a common reference (e.g. the fundamental voltage).
The most significant harmonic orders in three-phase distribution networks are the odd orders (3, 5, 7, 9, 11, 13 ….). Triplen harmonics (order multiple of 3) are present only in three-phase, four-wire systems, when single phase loads are connected between phase and neutral. Utilities are mainly focusing on low harmonic orders (5, 7, 11, and 13). Harmonic amplitudes normally decrease as the frequency increases. Sufficiently accurate measurements are obtained by measuring harmonics up to order 50. PRDC® provides the service to know the harmonics for customers, utilities, solar PV and Wind farm owners.
HARMONIC MITIGATION
In simple terms, harmonics are extra frequencies that when present in an electrical circuit, distort the AC sine wave. The distorted current waveform created by non-linear loads can cause many problems in an electrical distribution system. The effects of harmonics include: Voltage distortion like Excessive temperature rise in motors, Electrical noises, Sensitive electronic equipment malfunction; Increase in the apparent power and over-sizing of sources, capacitors, cables which enable de-rating of electrical equipment or over-sizing, accelerated ageing of equipment; flow of current in the neutral conductor which causes excessive temperature rise in transformer and tripping of circuit breakers.
PRDC® provide services by measuring the harmonics and performing the harmonic analysis based on the type of the installation and system. Based on harmonic analysis the best possible harmonic mitigation solution will be provided. The harmonic mitigation solutions include: inductors, capacitors, passive harmonic filters and active harmonic filters, phase shifting transformers etc. PRDC® provides the design specifications for harmonic mitigation devices based system specific harmonic analysis.
VOLTAGE & FLICKER MEASUREMENTS
The voltage flicker is a result of varying nature of reactive power demand of loads. Due to the varying nature of reactive power demand, poor performance is observed in lighting and other voltage sensitive loads. Typical loads causing voltage flicker include fluctuating loads like Electric arc furnace, rolling mill loads etc. or starting of large induction or synchronous motor etc.
In case of violation of flicker limits, solution involving necessary reactive power support as close to the loads causing the flicker is to be suggested for preventing the rest of network experiencing from voltage flicker phenomenon.
We undertake flicker measurements followed by detailed transient simulation studies to arrive at various options including the type of compensation, size and location required to mitigate the voltage flicker in case of observed voltage flicker is exceeding the permissible limits as per stipulated standards.
PSS TUNING
Power system stabilizers (PSS) have been extensively used in power systems as a very effective means to provide damping control for electro-mechanical oscillations (from 0.1 Hz to 2 Hz). Successful application of power system stabilizers depends on the careful design of its functional structure and regular tuning of its parameters in order to accommodate the ever changing and evolving system characteristics and conditions. To provide effective damping and ensure the stability of the system, the PSS should be carefully tuned. The tuning process is a topic of big interest for excitation systems and PSS manufacturers, who should complete the commissioning of a controller with a suitable and robust tuning according to the specific generator where the PSS is added and to the different operating conditions of the system.
Two PSS tuning objectives are available to suit different applications :
- Tuning for individual generators. This focuses on tuning PSS for specified generators for damping improvement of all modes associated with the generators.
- Tuning for inter-area modes. This computes all inter-area modes in a specified frequency range and then identifies the generators that have best controllability to the critical modes. PSS will be tuned on these generators to achieve the best possible damping to the modes.
FAULT RIDE THROUGH COMPLIANCE OF RE
Large scale of wind power has been installed in everywhere around the world. Both the wind farm installation capability and the wind turbine capacity have increased rapidly. There are many constant speed wind turbines using stall control with squirrel cage induction generators installed in the wind farms. Newly installed wind turbines are dominated by variable-speed wind turbines using pitch control with doubly fed induction generators and direct-driven permanent-magnet synchronous generators.
Power system operation with increasing wind power penetration will become more and more difficult. More conventional power plants will be replaced by wind farms and accordingly the stability of the power system will be affected. So the new grid codes have proposed even strict requirement to the wind power. Not only the wind turbines should be kept connection in grid during the fault and fast recover power generation after fault clearance, but also the wind turbines or wind farm can provide the voltage support and generate capacitive reactive power.
SUB SYNCHRONOUS RESONANCE & MITIGATION
Subsynchronous resonance (SSR) is one of the power system dynamic phenomena and its occurrence is of interest in power system networks where series compensated transmission lines or HVDC transmission systems are in the vicinity of a turbine generator. In series compensated networks, resonance characteristics of the network may vary significantly based on the topology and short circuit levels of the system. The frequency range of Sub Synchronous Oscillations (SSO) varies from 10 Hz up to 50 Hz. It has been known that the system is expected to be more prone to SSR interactions for a radial configuration i.e. those contingencies which result in the turbine-generator feeding radially to the lines with the series capacitors. Hence, PRDC® performs the analysis for different network topologies/configurations by considering such combinations of contingency of network elements which tend to make the series compensated network radial with the Thermal generation.
Based on the kind of interaction between mechanical & electrical systems and on the kind of disturbances considered, SSR phenomenon manifests itself in following forms:
- Induction Generator (IG) Effect (Self-Excitation)
- Subsynchronous Torsional Interaction
- Transient Torques
PRDC® also provides the services to find the vulnerability of wind farms to Sub Synchronous Oscillations (SSO) due to nearby series capacitors and recommends the mitigation or protection solutions based on the network configuration.
The following electrical equipment’s are at more risk due to SSO :
- Electrically closer to series capacitors.
- Long shaft / multi-mass generators (Coal, NG Steam and Combined Cycle).
The state of smart grid deployment covers a broad array of electric system capabilities and services enabled through pervasive communications and information technology, with the objective to improve reliability, operating efficiency, resiliency to threats, and our impact to the environment.
Distributed energy resources : The ability to connect distributed generation, storage, and renewable resources is becoming more standardized and cost effective to the consumers as well for the utilities. Several other concepts associated with a smart grid are in a nascent phase of deployment and includes the integration of microgrids, electric vehicles, and demand response initiatives, including grid-sensitive appliances. For successful integration of these smart grid initiatives, it is important to analysis the grid integration issues with high penetration levels of renewable generation at distribution level, impact and analysis of EV’s and demand response programs. The issues in RE integration include how to manage the voltage rise at distribution system, how much renewable penetration (like solar PV generation) can be allowed to connect to grid, impact of harmonics due to added renewables, impact of demand management, impact of electrical vehicles etc.
Electricity infrastructure : The smart grid areas that fit within the traditional electricity utility business and policy model have a history of automation and advanced communication deployment to build upon. Advanced metering infrastructure is taking automated meter reading approaches to a new level, and is seen as a necessary step to enabling dynamic pricing and consumer participation mechanisms.
Though penetration of these systems is still low, the growth and attention by businesses and policymakers is strong. PRDC® provides the services required electricity infrastructure for enabling smart grid environment by performing system studies at transmission level and distribution level. PRDC® also provides the services for preparing DPRs for transmission and distribution substation automation and the requirement of information exchanged with control centers. DPR also consist of Cost/benefit thresholds which are now encouraging greater levels of automation at the distribution substation level. With the addition of smart grid technologies every utility want to the change in reliability of the supply. PRDC® provides the services for smart transmission system by analysing the requirement of optimal PMUs and FACTS devices for national level transmission network. At distribution end, PRDC® provides the reliability indices based on distribution system reliability analysis for both conventional distribution system and smart grid systems where renewables and smart grid technologies are integrated.
Business and policy : The business cases, financial resources, paths to deployment, and models for enabling governmental policy are only now emerging with experimentation. This is true of the regulated and non-regulated aspects of the electric system. PRDC® provides the state of art guidelines and regulations for smart grid operational procedures. Also provides the cost best analysis for installation of solar PV panels.
