Greenfield Design and Predictive Maintenance – Two keys to achieve Power Quality

Power Quality (PQ) is often characterised as the electrical network’s ability to supply a clean and stable power flow that is always available, has a pure noise-free sinusoidal wave shape, and is always within voltage and frequency tolerances. However, deviations from these ideal conditions are frequent in most networks as the number of loads imposing disturbances is increasing rapidly. Poor PQ is an issue for a wide number of sensitive business & industrial sectors, common masses and its cost is high and rising as the number of disturbances are increasing. The need for an ideal PQ scenario has been growing for decades, owing to the increasing electronic equipment and gadgets in use. These devices with low immunity level, in turn, are also the most sensitive to disturbances, prompting the need for clean and stable power. Ironically, it is often an equipment itself that generates the disturbances. U.S. companies spends an estimated $26 billion on electrical power related issues each year. In EU, the cost is around 10 billion euros yearly and the spending on counter measures is less than 5% of that number. In India also, the loss suffered due to poor PQ is enormous, although it is still not well assessed.

Poor PQ and the need to have clean power for the informatics infrastructure are the two hard realities of today’s electronic age in India. Moreover, the perception and requirement of PQ varies across different customer categories and also are contingent on their dependence on power usage, and its impact on their productive output. A popular proverbial saying ‘A stitch in time saves nine’ is true even for having a good PQ environment. A little preventive and timely maintenance can eliminate the need for major repairs later. This blog focuses on the need for methods like Greenfield Design and Preventive maintenance to minimize the losses due to growing PQ issues.

NEED OF CONSIDERING HOLISTIC GREENFIELD DESIGNAPPROACH FOR PQ IMPRVOEMENT

The electricity network planning is highly customized primarily due to conditions of supply area, its design, construction, load demand, geographic distribution, technical standards, etc. To meet with the growing power requirement, the sector is expected to expand its grids over the next few years and managing PQ requires integrated and holistic greenfield design approach (i.e. proper initial planning, designing, commissioning to regular monitoring& measurement). This can prove to be beneficial in avoiding customer dissatisfaction, major equipment failure/damage and its associated costs. So, instead of falling easy prey to PQ challenges, following ideal strategy can minimize them. Moreover, these will help in providing stable supply of power and improve the efficiency of the electrical equipment.

  • Designing robust electrical system increases an equipment durability and also prevents potential intermediate failure. Infrastructure is generally the main reason for major PQ issues for utilities & industries, which has not been upgraded with ever increasing demand. They should upgrade and design the network in order to accommodate the market trend and new technological innovations.
      – Electrical System Design plays a major role in maintaining the reliability of an electrical equipment. A properly designed electrical system reduces sudden voltage or current alterations and facilitates for a smooth operation. At the same time, it also increases flexibility for future power systems with very high penetration levels from variable incoming sources.
      Wiring upgrade/Grounding: Proper wiring including upsizing such wiring system catering heavy loads and good grounding of entire facility is essential for electronic equipment to operate smoothly and also provide reliable power supply.
      Upsizing of equipment reinforces the distribution system to withstand the PQ issues. It means installing double-size neutral wires or installing separate neutral wires for each phase, and/or installing oversized or K- rated transformers, which allow for more heat dissipation.
  • Selection of right equipment with immunity: Among the various PQ mitigation steps, green field oversizing of distribution equipment, selection of higher PQ immunity of sensitive equipment, etc. plays a crucial role. Selecting the right fit is equally important to reduce critical issues like low susceptibility, low quality, distortion, etc. that it may have. Some of the examples to consider while choosing or designing equipment are:
      – Selecting a 12-pulse rectifier scheme of design instead of 6-pulse rectifier
      – Selecting Pulse Width Modulation (PWM) controlled inverter bridge instead of 3-phase bridge rectifier
      – Sizing the UPS/Inverter to load requirement and emergency generator, etc.
  • Deploying measures based on proactive assessment of possible PQ scenario: The techno-economic evaluation of PQ issues is one of the main problems the power system is facing. Therefore, its impact is even more cumbersome. There is a need of defined measures for bringing down the level of effect caused due to poor PQ. Some of them are mentioned below:
      Integrated design approach at initial stage can create a robust electricity system and its resilience to overcome poor PQ impact.
      Regular measurement of PQ parameters will reduce the risk of higher investment of device failures and other costs to considerable extent. Prior inspections can help analyze for any potential issues and their immediate solutions to avoid any major effect on the equipment/production life cycle.
      – Further, based on degree of vulnerability of system or process due to PQ issues, various types of power conditioning devices can be selected to protect the sensitive electronic equipment. Some of the power conditioning devices include Surge Suppressors, Voltage Regulators, Isolation Transformers, UPS alone or UPS with auxiliary generator, Noise filters, etc. These devices are highly recommended since unplanned disturbances on the electric utility’s system will occur. In the long run, power-conditioning equipment can provide very effective and inexpensive insurance. However, remember that even the best power-conditioning equipment cannot always compensate for faulty wiring and grounding.

PREDICTIVE MAINTENANCE – A KEY TO EQUIPMENT PERFORMANCE &POOR PQ MITIGATION

“All Systems Will Fail, The Only Question Is When, And How Frequently” – The statement clearly implies its importance in today’s modern industries moving towards 24/7 production schedule. The supporting equipment and systems continuous availability is the need of the hour for these industries. No longer do maintenance department have the luxury of extended periods of available equipment downtime in order to carry out maintenance, instead the maintenance function is moving toward a more Predictive Maintenance (PdM).
Unlike a traditional electrical maintenance (i.e. reactive, preventive, etc.), PdM focuses on a small set of measurements that can predict power distribution or critical load failures. Typically, the existing PdM inspection route includes equipment like motors, pumps, generators, gearboxes, etc. With little incremental labor and costs, power quality parameters like voltage stability, harmonic distortion, and unbalance can also be taken and recorded quickly. Current measurements can identify changes in the way the load is drawing. All of these measurements can be taken without halting operations and generate data points that can easily be entered into maintenance plan. Some of the basic power quality measurement guidelines for 3-phase equipment are:

Voltage measurements

– Phase-to-Neutral voltages
– Neutral-to-Ground voltages

Voltage sags

Phase to Neutral Sag count

Voltage harmonics

Phase voltage Total Harmonic Distortion (THD)

Current measurements

Phase currents

Voltage unbalance

Negative sequence, Zero sequence

Table 1. Basic power measurements for 3-phase equipment

Predictive maintenance enables industries to perform an effective amount of maintenance at an appropriate or practical time. Often referred to as condition-based maintenance, predictive maintenance tools monitor the condition of in-service equipment, either continuously (online) or at periodic intervals. One such tool is Infrared Thermography that has become more and more widely used for predictive maintenance. It takes advantage of the infrared radiation properties to extract useful conclusions for the condition of the equipment under test. It is neither non-destructive, nor an interrupting procedure and has no solid substitute. Some of its benefits include reduction in maintenance costs and unexpected failures, increase in uptime, etc. Technicians can quickly measure and compare heat signatures for each piece of equipment on the inspection route, without disrupting operations. Due to this, disruptions to facility operations can be reduced, since many PdM technologies are performed on in-service equipment. Having regular access to the current state of the equipment provides valuable information to determine when maintenance should be performed.

PdM provides cost-efficient solutions to maximize quality, reliability and enhance workplace safety. Monitoring the condition of equipment provides data to help anticipate and plan future maintenance activities, which saves times and costs in long run.

According to the US Department of Energy, independent surveys indicate the following average industrial savings when a functional predictive maintenance program is implemented:

  • 10 times – Return on Investment (RoI)
  • 25-30% – Reduction in maintenance costs
  • 70-75% – Elimination of breakdowns
  • 35-45% – Reduction in downtime
  • 20-25% – Increase in production

CONCLUSION

As an end user, we make significant investment in our equipment and appliances; hence it should also be our responsibility to protect those assets and ourselves against PQ related harm or any safety hazard arising out of this. Through regular inspections/predictive maintenance of the electrical installation, important steps like right planning and procurement of equipment at premise can help customer protect themselves against PQ challenges to a large extent. Therefore, rather than waiting for things to get worse and the PQ issues getting aggravated, we need to identify weak points in the electrical system and basic initial steps must be undertaken, to ensure a safe and reliable future for ourselves & our devices.

REFERENCES

(1) What’s your System’s Prognosis? – Richard P. Bingham, Nov 1, 2001

(2) Power Quality Monitoring: A changing market – Mark McGranaghan and Sandy Smith, Jan 1, 2002

(3) Applying power quality measurements to predictive maintenance

(4) Predictive Maintenance – The Key to Power Quality – David Bradley Rhopoint Systems Ltd March 2001 (Version 0b November 2001)

(5) Enhance Power Equipment Reliability with Predictive Maintenance Technologies – November 2012/1910DB1208 by S. Frank Waterer, Electrical Engineering, Fellow Schneider Electric USA, Inc.

(6) Power Conditioning Technologies, Questions on Electrical Earthing

(7) Applying infrared thermography to predictive maintenance – Fluke corporation

(8) IR Thermography in Maintenance – George Scroubelos,Executive VP, Dr. ACRM A.E. Chairman H&S Committee HMS and Avgoustis Tatakis, Electrical Engineer MSc., Level 1 Certified, Thermographer Greece