The Evolution Of Power Quality Standards And Regulations - Journey So Far And The Future

Published On: Sep 05, 2020

The formulation of standards and regulations is a function of patient and pertinent efforts. Consensus building is the biggest hurdle as well as decisive factor in defining the efficacy of the standard. Several forces are at play when developing the consensus on the standards and implementing it through appropriately framed regulations. To that extent, Power Quality standards and regulations world over can be said to have evolved and survived quite successfully. However, considering its beginning and journey so far, it would be apt to say that the PQ standards are still in their early life, perhaps the teenage where new transformations are underway in its physical, technological and experiential expressions. What lies in the adulthood, as the PQ standards evolve, remains to be seen?


Development of standards is a long-drawn process sometimes spanning over hundreds of hours. Take the example of valves, for instance, where the first need for the standards was made acute in the mid-1880s by the constant blasts and large number of lives lost at the Boilers which used valves with varying designs and manufacturing basis. The standards for valves continue to evolve after hundred years on the same lines – safety. Coincidently, about 100 years later to the initiation of valve standards, come the first attempts to formulate PQ standards – initiated in the mid-1980s. Fortunately, the need for Power Quality standards emanated from a relatively fatality free conditions. From the 1980s to today and into the future, the PQ standards have been and will continue to be the driving force for electrical power reliability.

In this blog, we take a look at the forces shaping the PQ standards in view of the general trajectory of their evolution over the three decades.


The development of portable Power Quality Monitor, as against sophisticated oscilloscope, holds an utmost importance in terms of developing the cognizance around PQ. Developed in the mid-80s, the portable PQ monitor triggered a wave of interest among end users who were then increasingly concerned about the constant disruption of power in their electrical network, allegedly caused by the poor PQ. The graphic reports in PQ monitors referred to as the signatures brought the hidden and often difficult to imagine nature of PQ in a visual form for the first time. It not just led to a greater interest and awareness but initiated an almost instant race among the manufacturers to develop algorithms and software to measure more and more electrical parameters.

PQ Measurement – developing the universal language
A fallout of these development has been a sort of double-edged sword. On one hand it has been driving the spurt in innovation and accuracy every few years through healthy competition. This is a very productive outcome. On the other hand, with so many suppliers collecting PQ data through various methods and using different techniques has also led to a slightly chaotic situation when it comes to assessment of PQ. This has been particularly counter-productive in driving the cause of improving PQ at end users right from the beginning. In fact, the difficulty can be credited to have driven the very first attempt to bring compatibility in the field of PQ measurement and monitoring with the formation of working group by Institute of Electrical and Electronics Engineers (IEEE) in 1987, for the development of a Recommended Practice, which culminated in 1995 with the publication of IEEE Std. 1159. Since then, the IEEE has followed the ‘working group’ model to develop and iterate the standards on PQ over three decades.

Much later, but more conclusively, following an initiative from the French and
the U.S. National Committees, the IEC Technical Committee TC77 came up with the development of a new standard on the measurement of power quality parameters. The IEC managed to build the much-required consensus among suppliers, end users and other stakeholders on the importance of obtaining reliable, repeatable and comparable data on PQ parameters, irrespective of the environmental conditions or instrument types. However, the process has been evolving further, making a steady and all rounded progress.

To summarise, the PQ measurement is still evolving on several fronts – the instruments, methods and contexts. The quest for a universal, interchangeable language on all these fronts has been fast evolving but not yet reached its conclusion.


The last two decades have witnessed and increasing focus on Power Quality. Clearly, this rise in interest and demand for PQ assurance has several important underlying causes. First, world over there is a shift from availability to reliability of power owing to increased penetration of power electronics in every use or application. As a result, there was a simultaneous propagation of the view that projected electrical power as a product whose assurance on quality was sought by buyers and sellers alike. Also, mostly because, both the buyers and sellers were themselves a part of polluting the power. Linked to this was also the fact that measuring and tracking PQ was proving to be a very effective way to reduce unexpected downtime and hassles and provide a clear rationale to prioritise the upgrade of distribution and transmission infrastructure.

Another factor that made it important to measure ‘quality’ was the deregulation of electrical power market. With entry of private players, accountability set in and the increased awareness meant customers demanding a better performance from suppliers. The monitoring of PQ also provided the basis for dispute resolution with transparency driving it, to unearth and bring to notice the underlying issues behind several common performance issues at the equipment, facility or grid level.

  • South America: In countries such as Argentina, Chile and Peru etc., typically, the legislation forces the supplier to deliver a good power quality level, or otherwise pay a penalty if the quality is outside the set limits.
  • In Europe utilities offer customised power contracts in which quality of supply is specified and penalties paid for performance outside guarantee.
  • Australia: Provides for compensation for damage caused by voltage variation outside set limits.
  • China: The national standards for PQ in China are divided into mandatory national standards (GB) and recommended national standards (GB/T). Products that do not meet the mandatory national standards specifications are prohibited from being produced, sold or imported. Whereas, the recommended national standards (GB/T) are voluntarily adopted through economic incentives/disincentives or market regulation.
  • India: Model PQ regulations have been issued by the central regulatory bodies such as Central Electricity Authority (CEA), Forum of Regulators (FoR) etc. National standard body issued voltage quality standards for distribution system. The same are being adapted by the state electricity regulatory commissions as per the assessment of local situation.

The one thing that stands common across all the countries that have taken different approaches is the need to measure PQ to a reference value.

The increasing need for PQ measurement has also led to the standards for measurement itself. The probabilistic nature of PQ has meant, the method of measuring PQ is equally critical. Together, the IEEE and IEC standards have been focused on describing the measuring methods and how the PQ parameters are calculated and interpreted.


The Institute of Electrical and Electronics Engineers Standards Association (IEEE-SA)

As a part within the IEEE that is instrumental in developing a global standard in a broad range of industries including power, IT/ITeS, Telecom, Healthcare, Manufacturing and Process and many more.

The IEEE Standards is currently the world’s leading standard defining body in electrical engineering and applications. IEEE has further established strategic partnerships with a wide range of standards organization and bodies around the world. The prominent among these include International Electrotechnical Commission (IEC), International Standards Organisation (ISO), International Telecommunications Union (ITU) etc. Off lately, several countries around the world have been adopting the IEEE standards as the guidelines in defining the standards in their country.

Some key publications and their updates by IEEE in context of advancing the standards for PQ are as below:

  • 446-1987 – Recommended practice for emergency and standby power systems for industrial and commercial applications, also known as the Orange Book
  • 241-1990 – Recommended practice for electric power systems in commercial buildings, also known as the Gray Book
  • 142-1991 – Recommended practice for grounding of industrial and commercial power systems, also known as the Green Book
  • 493-1997 – Recommended practice for the design of reliable industrial and commercial power systems, also known as the Gold Book
  • 1100-1992 – Recommended practice for powering and grounding sensitive electronic equipment, also known as the Emerald Book
  • IEEE 1159-1995 – Recommended practice for monitoring electric power quality

Here’s a handy list of various working groups formed by IEEE :

International Electrotechnical Commission (IEC)

IEC is the world’s first non-Govt body for electrical standardisation of technology. IEC was formed as an institution in ISO, but has continued to remain technically and financially independent. Today, IEC concerns itself with standards development work in electrical, electronics and various application areas of the same. IEC aims to promote the international unification of electrical standards. IEC has 81 member countries.

IEC has a relatively structured set of norms for measuring and monitoring PQ. As compared to IEC, the IEEE norms of PQ provide a balance of practical and theoretical background of the PQ phenomenon making it both universal in terms of use value across countries and also quite comprehensive in the process.

The key IEC Power Quality Standards include

  • IEC 61000-4-11 – voltage sag immunity – 16 Amps or less
  • IEC 61000-4-34 – voltage sag immunity – more than 16 Amps
  • IEC 61000-4-30 – power quality measurement methods

A summarised list of IEC Standards can be found at the link here:

The ever-evolving, overlapping set of standards

One key distinguishing factor for PQ standards is its fast and ever evolving nature as compared to other comparable standards. This is due to two primary reasons. First, the measurement and evaluation of electricity has to be performed at the instant of its consumption – a unique aspect for PQ. Secondly, the PQ measurement is complex in terms of the supplier and user, whose sensitive electrical equipment could also be the source of disturbances. This makes it quite difficult to separate the influencer from the influenced and arrive at specific values. In this view the standards have been specified at various locations.

Standard IEC 038b distinguishes between two different voltages in electrical networks and installations:

  • Supply voltage – line-to-line or line-to-neutral voltage at the point of common coupling that is main supply point of installation
  • Utility voltage – line-to-line or line-to-neutral voltage at the plug or terminal of the electrical device

For instance, the several IEEE standards specify the THD values measured consumption end at PCC and so on. On the supply side, the EN 50160 standard has emerged for voltage measurement. It focuses on characterisation of electrical energy in public distribution systems. From a regulatory perspective, the European Union has been a leader in developing and implementing quality of supply standards. The implementation of European Norm 50160 is a milestone in many ways. From many countries adapting the EN 50160 norms in their national PQ regulations to it influencing new technologies in instruments, the standard has charted a unique path for voltage measurement.

Power Quality Data Interchange Format (PQDIF)

Another key standard that matters for the future and a key to developing the universal common ground for PQ measurement/monitoring is the 1159.3-2019 – IEEE Recommended Practice for Power Quality Data Interchange Format (PQDIF) –

The PQDIF specifies the file format suitable for exchanging power quality related measurement and simulation data in a vendor independent manner is defined in this recommended practice. The format is designed to represent all power quality phenomena identified in IEEE Std 1159-2009, IEEE Recommended Practice on Monitoring Electric Power Quality, other power related measurement data, and is extensible to other data types as well.


Developing a standard and regulation for a relatively abstract natured PQ is a challenge at several levels. The implications of poor or good PQ far reaching and often affect the competitiveness of the industry. At APQI, we have been of the view that PQ standards are in many ways a reflection of how the nation and society values ‘quality’ and therefore a determinant of the ‘quality of life’ itself.

PQ events can last only for microseconds and could happen sporadically. The same events can be extremely detrimental to the reliability of production in some facilities and be of no particular concern in some other facility. To “prescribe” a standard requires a complete picture and historical perspective.


PQ definition is nothing but a technical consensus. This involves multiple and overlapping stakeholder’s with diverse interests and hold over technical domains. The figure above represents how the PQ consensus evolves through the nation or a pressure group among all stakeholders. Arriving at a successful framework of PQ involves overlapping topics, draws on multiple expertise domains and emergence of integration points for consensus. That’s the key to triumph for PQ.


The development of regulatory frameworks often begins with minimum required standards. Point of view in the beginning is almost always to have a minimum qualifier in place where there is none. But this becomes quite tricky in case of PQ.

PQ is a local phenomenon. While the IEEE and IEC or EN standards specify the guidelines, the local data is vital to adaption of these guidelines in the regulatory framework.

The minimum standards must strike a balance – a very difficult one – to find the common meeting point for what’s possible? and plausible?

For example, several factors have to be considered in striking the balance:

  • Not to impose an unreasonable stringent limit
  • Ensuring a funding mechanism is put in place to meet the limits of emissions
  • The probabilistic nature of PQ is adequately considered in measuring the gaps w.r.t standards

The risk, as often experienced by policy makers, is that the below average industries driving and keeping the minimum standards line always lower. Another aspect is then how to ensure that those with better PQ continue to stay invested in improving the PQ.

For instance, network specific nature of voltage dips could mean the minimum standards are easily met in some part of the country while creating the risk of distribution companies not investing any further in improving voltage quality. Contrary to this, there could be a situation where the utilities might invest heavily to control voltage dips in regions where the impact on customers is minimal to none.

It’s this classic catch-22 type situation that makes PQ regulatory implementation tricky. The key lies in continuous monitoring and relative benchmarking – which again is a whole new way of setting the standards.

Some type of dynamic benchmark could be the future. This means the customers have to look at the PQ indices and continuously adjust their PQ characteristics to be on the good side of the field.


In the next few years, we can expect an expanded definition of PQ indices, clarity on roles and responsibilities of various entities, update of standards/limits to follow, and a new incentive/disincentive framework along with detail procedure to monitor/assess PQ.

Electrical energy will be considered as a product and its quality will have to assured based on standards and regulations. This will be a new normal for the electrical power in this decade. The contractual applications of PQ measurements as specified in IEC 61000-4-30 show the way to the future in this regard. The standard emphasizes the need for a continuous monitoring given the unpredictable nature of PQ parameters. Any temporary measurement will defeat the purpose of achieving the contractual obligations between stakeholders. Permanent monitoring will be the key to successfully tackle PQ issues.

The framework and implementation success of regulations with the emphasis to continuously improve PQ, even in areas of good performance, is the future. That is also a mark of adulthood!


  1. Voltage Characteristics EN Standards –
  2. The Evolution of Regulatory Power Quality Standards in South Africa –
  3. The National Standard of the People’s Republic of China for UPS systems –
  4. Power Quality Standards: An Industry Update –
  5. Power Quality Standards references of working groups of IEEE –
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