Published On: Dec 26, 2014

The importance of high power quality (PQ) electricity supply has never been greater than it stands today. In a conclave on ‘Challenges to Power Quality’ hosted by Bureau of Indian Standards (BIS) held in Oct 2013, the International community of electro technical experts shared concerns on Power Quality relating to India and other developing economies like China, Brazil, South Africa, etc. In a developing country like India, where the distance between generating stations and load centers is large, managing power quality for the overall energy spectrum is a major challenge. With the continuous and massive rise in sensitive electronic device usage in all walks of life, the paradigm is gradually shifting from ‘Availability’ of power to ‘Quality’ of power with “Availability” already a default expectation. The complexity and interconnectivity of our power networks has further aggravated PQ issues. Poor power quality not only creates disturbance in the grid system but also has financial impacts on a country’s economy.

While most utilities strive to provide continuous power, however they are now grappling with continued efforts to reduce losses (especially commercial and non paying subsidized consumer segments) with little or no incentive and hence interest in improving PQ beyond power factor corrections is at the most an intent. Providing continuous power supply does not end in delivering quality, it encompasses more. Hence, it is critical now that more initiatives are taken by regulatory/nodal bodies to take corrective measures for maintaining and measuring better power quality. First step for managing anything vital is to measure and that must be in place without any delay. The metering technology has leap frogged to meet such expectations in a sensible manner.

As per one of the research by International Journal of Emerging Technology and Advanced Engg [1], the global cost for poor PQ is estimated to be more than 500 billion euros (620 billion $) per year that is nearly 50% of the turnover of the global electricity sector. In fact, for many business uses, the cost of poor Power Quality is higher than the electricity bill and the cost is only rising.

This blog attempts to showcase that developing countries like India now need to develop favorable policies and measure PQ performance parameters on a continuous basis.

CURRENT POWER QUALITY SCENARIO IN INDIA

In the Indian scenario, Power Quality (i.e. continuity of supply, voltage and current waveform quality) comes along with the service associated of the electrical energy supply. Below table shows the key PQ indices, their status (defined or not) in Indian Grid Standards and their specified tolerance limits for all power entities:

Table 1. Key PQ Parameters and their regulation status in India (Read: Central Electricity Authority’s Detailed Grid Guidelines)

Government and various state regulatory bodies in India are required to measure reliability supply indices, , such as SAIFI, SAIDI, and CAIDI and monitor the interruptions on a regular basis. The same is also included in Aggregate Revenue Requirement (ARR) filed annually by utilities, however there are no or only may be few occasions where Regulator has incentivized or penalized discoms for non-compliance on these parameters. It is also essential to take cognizance of these reliability supply indices as being only a part of the overall quality of power which also includes the quality of voltage and quality of waveforms – standards and performance benchmarks on which are primarily missing.

With the new technological advancement and the desire to make the electricity network smarter and more efficient, the utilities key strategies remains ensuring reliability of supply, AT&C loss reduction and thereby improving Energy Efficiency. However, it is very important now to understand that Power Quality is not different from the strategies mentioned above for utilities. In fact, it is interrelated with and further facilitates the success of supply reliability, loss reduction and energy efficiency for utilities. There is a need to understand that improving PQ is nothing but ensuring continuity of supply. (See our earlier blog: ‘DE MYSTIFYING PQ: INTERRELATION WITH POWER SUPPLY RELIABILITY, AT&C LOSSES, ENERGY EFFICIENCY’)

However, there are no specific Supply Quality indices measured or reported even as there are standards and norms set, which are primarily related to customer service quality for some of the key PQ parameters at the Central level.

Need of introducing PQ standard in distribution sector in India

Above table 1 (i.e. key PQ parameters) clearly indicates that Indian Grid regulation is quite good for voltage level above 33kV. However, it does not address voltage level below 33kV i.e. distribution sector. This is due to CEA issuing technical standards only for transmission or grid domain being empowered by Act, but leave distribution for States to handle. Distribution is the key segment in the power value chain and cannot be ignored, as considerable percentage of the PQ issues gets generated from customers (like high tech industries, bulk customers with significant nonlinear loads, etc.). Although various SERCs and Discoms has successfully introduced state level Standard of Performance, however there is need that CEA takes proactive steps to give Technical Guidelines to SERCs, which are then being measured and monitored on a regular basis.

Another main and important standard that is missing in the guidelines is the amount of current harmonic an individual customer injects into the utility network. The current limits are based upon the size of the consumer relative to the size of the supply. The relative size of the load with respect to the source is defined as the short circuit ratio (SCR), at the point of common coupling (PCC), which is where the consumer’s load connects to other loads in the power system. There are international IEEE 519 standards that have specified current limits for individual harmonic components as well as total harmonic distortion.

In addition to current harmonics, transformer heating, voltage flicker are some of the PQ issues caused by individual customers and their standards are missing and need immediate intervention at regulatory level to address them. This is more exigent since distributed generation is taking deep dive for integrating with conventional grid transforming into smarter grid of future.

STEPS/INITIATIVES TAKEN BY OTHER COUNTRIES TO IMPROVE POWER QUALITY

Developed countries like that of USA and Europe, who have comparatively stable power supply, have recognized the PQ risk, and been working for its mitigation for last almost two decades. The Council of European Energy Regulators (CEER) is a not for profit organization in which Europe’s national regulators of electricity facilitate the creation of a competitive and sustainable market for electricity in Europe. Based on CEER’s benchmarking report on Quality of electricity supply in 2011, 18 countries already having an operational voltage quality monitoring system in place. The number of voltage quality monitors in operation in the public distribution and transmission networks has seen significant growth in recent years, largely due to a number of technical developments. The cost of monitoring equipment has dropped significantly, making it less of a barrier for installing a larger number of them. At the same time, their performance has increased. In fact from a regulatory perspective, the European Union has been a leader in developing and implementing quality of supply standards through its implementation of European Norm EN 50160. Many countries have used EN 50160 as the basis for their national quality of supply regulations.

Some of the initiatives taken by other countries to improve PQ scenario within their distribution utilities are mentioned below:

BRAZIL ELECTRICAL SYSTEM

Until mid-90s, there has been inefficiency in Brazilian Electrical System. Further, at that time there was no PQ standard. In early 2000 as part of restructuring process, the national electric system in Brazil defined the regulation and Grid Procedures for utilities. The PQ standard was divided in quality of service, sustained interruptions, quality of products, in addition with steady state and transitory phenomena.

Considering the size of the Brazilian Electrical System and cost sensitive market, an economically viable PQ meter and monitoring system was developed and implemented on a low cost basis. Each PQ meter device is installed in specific points of common coupling and computes PQ indices of the electrical system. The steady state measurement is performed in intervals of 10 minutes at points of common coupling and the measurement period is one week or 1008 intervals. An interruption or sag/swell voltage occurrence within an interval will invalid it. The measurement process continues until the valid 1008 intervals are obtained. At the end of measurement, these disturbances are eliminated and analyzed independently.

It is worth mentioning that the focus was more on Voltage regulation and its related PQ indices like harmonic voltage, unbalance, sag & swell, fluctuation, etc. These steps are helping the country in maintaining PQ database while continuously building more knowledge, further refinement in methodologies or compliance limits for PQ improvement.

SINGAPORE’S ADOPTED POWER QUALITY SOLUTIONS

PowerGrid Ltd, a subsidiary of Singapore Power Ltd, is responsible for the transmission and distribution of electricity in Singapore. With the increasing presence of high tech industries in Singapore, it has become new challenge on the deliverables of supply, particularly power quality in terms of voltage dip. Although PowerGrid strives to minimize the causes of voltage dips from the network end by following code of standard performance, there is no technology to produce equipment or cables that do not fail. Hence, the next best thing is to focus on effectively mitigate the impact of voltage dips on voltage sensitive plant equipment. Below mentioned are some of the initiatives from the plant end side for mitigating PQ solutions:

• Incoming Supply Intake: At the supply intake level, PQ solutions such as Medium Voltage UPS, Dynamic Voltage Restorer (DVRs), etc. can provide protection for the entire plant. Medium voltage devices do not come cheap, however it overprotects the plant protecting both sensitive and non-sensitive loads.
• Equipment Controls Level of the voltage sensitive equipment: This has been recognized as the most cost effective mitigation solution. However, to apply PQ solutions at the controls level of the equipment, sufficient knowledge on the characteristics of the equipment during voltage dip is required. The main advantage of implementing PQ solution at this level is lower cost, which can be relatively small compared to the supply end solution. PQ solutions like Dip Proofing Inverter (DPI), Momentary Line Protector (MLP), Constant Voltage Transformer (CVT), etc. are some of the low voltage mitigating devices.
• The voltage dip test: set serves as a powerful diagnostic tool for determining the ride- through characteristics of industrial processes and voltage-sensitive equipment when subjected to voltage dips. PowerGrid has conducted voltage dip tests jointly with customers and equipment manufacturers to determine the controls susceptibility level of voltage-sensitive equipment. The information is useful to customers to better understand the performance of their equipment, and to make informed decisions on the type of mitigation devices to harden their equipment.

CHINA’S POWER QUALITY

With the continuous increase in China’s power system over the last 30 years, there has been various PQ challenges in China. Some of the key challenges are mentioned below:

• Long distance between generating sources and load centers, bulk transmissions
• Significant increase of disturbing sources: harmonics, unbalance, voltage fluctuation, flicker, etc
• More customers sensitive to power quality due to computer, PLCs, automated controller, etc
• Rapid Development of Renewable energy integration: power flow fluctuation, stability, harmonics, etc.

To cope with the above challenges, in between late 1990s and early 2000s, the State Grid Corporation of China (SGCC) produced standards on ‘technical supervision of grid power quality’ and ‘voltage quality of the power system’. Compliance limits are applied at all voltage levels. The national standards are based on International Electro-technical Commission (IEC) including measurement methodologies, compliance limits, and PQ monitoring product requirements. IEC 61000 series standards in power quality have been widely used in China’s power industry and identically adopted by Chinese standards (GB/T, GB/Z). In comparison with EN 50160, Chinese standards addresses some key limitations as mentioned below:

• The GB/T standards have higher compliance limits on frequency, rapid voltage changes, flicker, temporary over voltages and low-order harmonic voltages.
• Dips, swells and interruptions still do not have compliance limits.
• Steady-state parameters have compliance limits for 100% of the measurement period, with the exception of mains signaling voltage.

Although there has been considerable development/steps taken in China on the concept of power quality, still more new standards to be developed. In a recent conclave in New Delhi on ‘Challenges in Power Quality’, Dr. Yinbiao Shu, President of SGCC and also as Vice President of IEC team clearly mentioned that ‘Strict compliance with IEC equipment standards is fundamental to securing power quality’, followed by consistent and accurate data monitoring, thereby allowing PQ supervision at the global level.

While the rising/developing countries like Brazil, China, South Africa, etc. have undertaken various PQ initiatives, they need to further strengthen the regulation limits and monitor PQ indices regularly, in addition to other electrical indices.

IMMEDIATE NEED FOR INDIAN REGULATORS TO MEASURE AND MONITOR PQ INDICES

Quality of power is next level of efficiency in the power system. Central and State Energy Regulators are statutory bodies that govern reforms of power sector in India. They form policies regarding power management for utilities and customers. Maintaining good power quality is incumbent not only on the part of utilities but also customers. In India, however, utilities haven’t matured on the PQ concept and mostly the concept is mixed up with reliability of supply. It is high time now for regulators to make provision for PQ measurement and strict adherence by their respective licensees. Although all state regulators have code of supply in Tariff Regulations, however it does not provide incentive/penalty mechanism related to quality of supply and hence utilities do not necessarily consider equally about continuity of power supply when compared with other priorities. Utilities could be compensated for the PQ investments made for laying up the infrastructure via ARR petitions.

At the same time, customers need to be educated on PQ issues so that their facilities can be designed to improve PQ environment. Another important stakeholder in PQ improvement are the Original Equipment Manufacturers (OEMs). They should be aware of PQ norms and consider the same in design of their equipment. OEMs must clearly understand the customer’s loads and design the equipment with more tolerable limits.

Further, lack of appropriate data and quantification adds to the woes of PQ issues. With limited or no data, the utilities are unable to take right steps to mitigate it. A sound and transparent mechanism is required to measure and obtain correct data.

For example, in June 2013, Tamil Nadu Electricity Regulatory Commission (TNERC) in its Tariff schedule has imposed strict penalties on HT customers for harmonic level violations beyond the permissible limits specified by CEA regulations. The customer is liable to pay compensation at 15% of the respective tariff. The Licensee shall measure harmonics using standard meters / equipment in presence of customer or their representatives.

Summarizing all, there is a need to place a comprehensive power quality improvement plan to meet the needs of high tech industries. The plan could cover following PQ initiatives:

• Power Quality indices measuring and monitoring system
• Dips, swells and interruptions still do not have compliance limits.
• Application of cost effective mitigation technologies
• Reactive power management
• Network Enhancement
• DT and Cable damage prevention
• Incentives for customers in power bills can be improvised for maintaining harmonics at prescribed limits as per standard and penalties for not maintaining it

CONCLUSION / NEXT STEPS

The cost of poor PQ is high and rising. PQ issues are very much important for utilities, end users and it is essential to be known by the concerned regulatory authorities and users for reduction of economic losses due to the poor PQ. One of the apparent reasons of poor PQ is also the lack of awareness and knowledge about the topic. Therefore, in order to make utilities and customers contribute to PQ improvement, onus is certainly on the regulators to promote and support through policies.
With the ongoing regulatory, policy and tariff structural change in the Indian electricity industry (following the Electricity Act 2003), the issue of PQ is poised to become a figure-of-merit amongst the competing distribution utilities. Improvement of PQ has a positive impact on sustained profitability of the distribution utility on the one hand and customer satisfaction on the other. Improved Regulation, policies, standards & end-customer awareness and reinforcement will play key role in guiding market for optimum equilibria for good PQ environment.

REFERENCES

1. 1. Power Quality Issues and Need of Intelligent PQ Monitoring in the Smart Grid Environment – International Journal of Emerging Technology and Advanced Engineering, Sep 2012
2. The New Brazilian Power Quality Standard and a Low Cost Device Meter– Department of Electrical Engineering, March 2013
3. PowerGrid Ltd, Singapore – Leonardo Energy
4. Determination of Tariff for Generation and Distribution – TNERC, June 2013
5. Quick comparison of Quality standards of different countries – Schneider Electric
6. Network and plant-end power quality solutions – PowerGrid, Singapore
7. Challenges of Power Quality – 77th IEC General Meeting, New Delhi