Impact of Seasonal Variations on Electrical Demand and Power Quality - A Challenge That Needs Attention

Published On: Apr 10, 2019


The power quality in low voltage grids is affected by several internal and external factors. While there is elaborate assessment of variations in factors concerning internal electrical environment (type of electrical load, power generation sources etc.), the impact of external environment variations (climatic and atmospheric changes) gets scarce attention.

INTRODUCTION

The dependency of electrical consumption demand on weather in India has increased significantly. The most obvious sign is the huge increase in the electrical load with rise and drop in mercury in the summers and winters. Electricity use varies with the weather primarily due to the change in demand for space heating/cooling depending on the seasonal changes in temperature and humidity. The characteristics and magnitude of such connected loads often lead to a high and mostly an adverse impact on the power quality. The usage of these loads by the customers varies in different regions as per the season. Studies have observed that vital PQ parameters such as voltage tend to show a significant variation triggered by changes in demand during different seasons.

A study published in “Global Trends in Urban Cooling and Heating” May 20, 2015 interestingly finds that majority of Delhi’s electrical demand is from the comfort loads. Even more alarming is the fact that over 50% of the annual electrical consumption in Delhi is dependent of temperature and this is found to be very large in comparison to some of the most affluent cities in the world such as New York city, Tokyo, Los Angeles, Singapore etc. A similar picture could be expected across several other Indian cities, given the commonalities of large urbanizing population base, increasing temperature in the cities and tropical climatic changes necessitating use of artificial cooling and heating devices.

Given the huge change in load patterns, across seasons, there is an urgent need to understand and address the impact on PQ. This article explores different aspects of the challenge of poor PQ arising from the significant seasonal changes in electricity demand.

LOCATING POWER QUALITY IN SEASONAL VARIATIONS

Reliable electric power is not a luxury anymore. Given the dependency of electrical and electronic devices, it will not be an excess if ‘reliable electric supply’ is termed as being critical to well-being of humans. To that extent an electrical outage, especially occurring due to a seasonal variation in power demand, puts a challenge to well-being and health of the population. From a seasonal variation perspective, the shortage of electric power generation or sequence of faults in the distribution network are key causes of disruption of electrical services. While electrical networks are built with multiple redundancies, climate induced environmental changes impacts several areas. Given below are some typical scenarios that disturb the power quality in the electrical network.

Seasonal Changes Impact Area Nature of Impact PQ Implications
Temperature Increase Power Generation Lower generation efficiency, lower PV efficiency Increases the chances of minor PQ disturbances such as long interruptions, voltage sags etc.
T&D Reduced carrying capacity of Cables and Transformers Increased loading from heavy inductive loads such as motors etc.
Higher T&D losses Chances of greater faults in the network due to pre-existing PQ events
End User Peak Loading Heavy loads such as AC Motors leading to poor voltage
Higher precipitation T&D Risks to electrical infrastructure – especially earthing, damage to power lines etc. Poor PQ triggered by less reliable and safe functioning of electrical infrastructure


While the direct impact of changes in external environment is visible in terms of increased energy demand, utilities and large end users must study the PQ implications carefully. Most often, the gaps in meeting the electrical power demand will bring to surface certain PQ disturbances which were previously not observed. In an already weakened electrical network, these PQ issues can pose additional challenges.

COMMON PQ DISTURBANCES OBSERVED WITH SEASONAL CHANGE

Voltage variation (generally low voltage) is the most prominent phenomena observed with the onset of summer season. The long term voltage variations that typically last for several seconds are typically observed. These variations are not due to faults in the system but mostly owing to load variations and system switching operations. The long term variations further induce under voltage or over-voltages, depending on the variation. The impact can adversely affect the functioning of sensitive equipment, especially the voltage controlled equipment such as motors, lights and Air Conditioner loads.

The impact of seasonal voltage variations are particularly discomforting for the household consumers. The common electrical disturbances, occurring due to internal network and grid or power supply related issues, often lead to malfunctioning, poor performance or life of equipment for its users. Here we discuss key PQ events that are typically observed with change of weather.

Voltage Sag

Voltage sags are characterized by a sudden voltage drop below the recommended level for a short or long duration (from a voltage cycle to up to a min). Typically, voltage sags are observed with switching of equipment that need a relatively larger start-up power. Examples include motors, refrigerators, ACs, Heaters etc. Poor connections or weak transformers further add to the PQ issues, especially, when a large number of consumers switch on such heavy loads almost simultaneously.

Voltage Surge

Turning off of heavy loads such as an air conditioner or electric motor used to pump water are not free from problems either and often leads to power surge. This occurs due to sudden drop in the large voltage that these equipment draw when in operation, thus creating a disturbance in the steady voltage. With a surge in use of such heavy loads, especially in summer and winter seasons, power surge is a common phenomenon in specific time zones (the morning rush hours, for instance). House hold consumers rely on various equipment such as UPS, Voltage stabilisers to protect their equipment from such phenomenon. In fact, highlighting the risks, OEMs are aggressively promoting such accessory equipment with their products as a standard attachment.

Brown outs

Steady decline in voltage is observed during peak load times (most prominently in the summer season) when the power distribution companies reduce the voltage level. Dim lights, non-functioning or sub-optimal performance of ACs, Heaters etc. are typically observed during brownouts. Long duration of brownout can lead to damage of parts in these equipment, adding to maintenance or reducing the life of these equipment.

Power Spikes in Monsoons

Sudden or very large increase in voltage is observed during lightning and thunderstorms. Lack of appropriate protective devices, poor cabling or earthing etc. can lead to fatal results in the scenario of a power spike. Power conditioners and suppressors are recommended to ensure protection of equipment and prevention of any safety hazard such as electrical fire, short circuit etc.

FIXING POOR PQ AND AVAILABILITY – WHO’S JOB IS IT ANY WAY?

With one of the highest peak demands in summers, subsidised tariffs and rapid urbanisation, Delhi makes an interesting case in analysing seasonal variations in power availability and PQ. Referring back to the example of Delhi, the studies comparing the electrical demand change in the region are alarming.

  • Electricity consumption in Delhi has grown by almost 42 per cent between 2006-07 and 2017-18.
  • Peak demand has grown by staggering 64 per cent between 2006-07 and 2017-18.
  • On an average, an electrified household in Delhi consumed about 260 kiloWatt-hour (kWh) of electricity monthly in 2016-17, (approximately three times the national figure of 90 kWh and equivalent to the consumption of an average German household)

Source: Why is Delhi’s electricity demand rising so rapidly? – CSE

https://www.downtoearth.org.in/news/environment/why-is-delhi-s-electricity-demand-rising-so-rapidly–60831

In Delhi particularly, subsidised power tariff, badly designed units (from a cooling and energy efficiency point of view), significant rise in ambient temperature and cheaper consumer appliances has fuelled an unparalleled spike in power demand. Given the peak demand of Delhi nearing 7400 MW in the May-June period, energy efficiency and DSM continues to be the biggest concern. However, given the poorly designed infrastructure and lack of professional workmanship, worsening PQ is also at play, albeit as a strong undercurrent.

The figures at national level are not encouraging either. Take for instance, that between 2013 and 2018, India produced over 26.5 million AC units, of which about 60 per cent were 3-star. A report from IEA estimates a 15-fold jump in demand for power for space cooling by 2050. All these figures point to the definitive trend of only an increase in variation of demand and loads in different seasons. Whether its abysmal record of energy efficiency or worsened Power Quality, the question is who will own the responsibility to fix the problems arising due to seasonal variation of loads? Or it would only be convenient to blame the seasons.

A very broad overview of focus of various stakeholders indicates lack of synchronous efforts. While the power generation companies are focused on securing the resources (coals etc.) for serving the peak demand, power distribution companies are essentially concerned about the demand management and bidding for the cheapest power. Given the lack of regulatory and manufacturing standards, Consumers are being increasingly lured by offers to buy energy intensive, sub-optimal appliances by the manufacturers.

Shift to Renewable Energy – a concern for PQ

Another key concern for PQ is the strategies deployed to absorb the gap in demand variation involves large-scale use of renewable energy for distributed energy generation.

  • Gujarat has generated 1.2 million kilowatt hours of solar power from a rooftop solar project in the capital Gandhinagar
  • Karnataka plans to add rooftops alone will contribute 400 megawatts by 2018
  • Chhattisgarh government had decided to set up 51,000 solar powered irrigation pumps by the year 2019
  • By the end of the Financial year 2017/18, Odisha has set a target of achieving 297MW of total solar installed capacity, with 125MW coming from rooftops

However, without proper measures at the inception stage itself, both wind and solar power have been found to adversely affect the PQ in the electrical network. Further, the impact of problems arising from the seasonal variations in renewable power and load on the electric power grid is still not fully visible in many cases.

CONCLUSION

Given the widening seasonal variation in the electrical load, mostly non-linear in nature, demand patterns, consumers are likely to experience a rise in the Power Quality problems.

Just as non-availability of power was considered as normal in Indian cities about 5-7 years ago, seasonal variations could lead to consumers being left susceptible to poor PQ environment as the new normal.

Synchronous efforts by all the stakeholders (including the consumers) with the common goal of providing ‘quality power’ is the key. However, given the reactionary approach to PQ, at the moment, such an effort seems to be a distant possibility.

As the consumers continue to invest in protective equipment to minimise the risks from poor PQ, the scale of problem is likely to only rise in near future. While the current approach minimises the potential of short-term harm to consumers, shields the distribution companies from committing to PQ and continues to boost the sale of protective equipment such as voltage stabilisers, UPS etc., in the long-term, it only means much higher costs for everyone.

REFERENCES

  1. Analysing the Electricity Demand Pattern – POWER SYSTEM OPERATION CORPORATION LIMITED, NEW DELHI, INDIA

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