Selective Load Shedder

An initiative for Codestorm – Apphack, Wipro - 2015

By Team Tremors:Sourav BiswasSudip BhaktaSayan Chakraborty

Introduction

Demand for energy is increasing

Energy will run out in the next 50 years

Power outages would strike except those running on solar or non-conventional sources

The Catch 22 Situation

Scenario

In power supply networks, the power generation and the electrical load (demand) must be very close to equal every second to avoid overloading of network components, which can severely damage them. Under certain conditions, a network component shutting down can cause current fluctuations in neighboring segments of the network, though this is unlikely, leading to a cascading failure of a larger section of the network. A rolling blackout, also referred to as load shedding, is an intentionally engineered electrical power outage.

In India, in 2004-05, electricity demand outstripped supply by 7-11%

The net effect of such ever increasing demand to generation ratio are driving electricity prices higher and the factors responsible are heavy use of air conditioning due to the extremely hot weather; annual refurbishment programmes which had taken a number of stations out of service; unplanned "outages" at a number of sites; and a shortage of electricity imports from neighbouring States/Countries. Nuclear based electricity generating stations are running on low generation at times, as they run short of water to cool its nuclear reactors. The Energy management in many countries is in a total mess and needs corrective measures to come out of this Catch22 situation.

Analysis of the problem

In urban, semi-affluent households, the average load consumption is around 4KWh with HVAC/Air-conditioning occupying 70-80% of load demand for cooling and ventilation. The load demand for HVAC is not uniform over the 24 hour period and mainly surges during morning hours and at night when the household is fully occupied. The rest of the day when most people are at work the load demand depreciates considerably. Let us see the Daily Load curve for New Delhi as shown aside.

Our Approach to the Problem The solution to this problem is outright and simple. We have to dynamically regulate

urban loads to cut down on energy demand and prevent outages or rolling blackouts.

We restrict and restructure the usage of various equipment at different times of the day to control the instantaneous load demand and bring down the average load demand of the entire household.

The wonder gadget to implement the scheme is a Selective load shedder system (SLSS) with GSM-GPRS/CDMA connectivity installed in the household that dynamically controls the multiple power circuits intended for the various machines running in the household.

The Utility Company constantly monitors the load demand to match the electricity generation and sends control information over the Internet to dynamically control the household load demand by enabling or disabling the power circuits on the SLSS installed in the urban households. When the electricity generation is low, we reduce our demand by cutting down on the air-conditioning devices and other power hungry gadgets; when the generation is in surplus the peak load demand can be allowed.

Working Flow:

HTTP Packet detailsThe parameters to be transmitted from the mobile device is as follows:

Preloaded device-id of the device.

The Latitude and Longitude of the area.

The syntaxes used in the Http get packet is as follows:

Device-Id: id=100

Latitude: lat=17.23546

Longitude: lon=78.53564

Example: http://comkits.com/processor.php?id=100&lat=17.23546&lon=78.53564

The http response shall contain the following data:

Device-Id, Registration Status (0-Failure, 1-Success) 

The parameters to be transmitted from the mobile device is as follows.

Preloaded device-id of the device, The Latitude and Longitude of the area, The syntaxes used in the Http get packet is as follows:

Device-Id: id=100, Latitude: lat=17.23546 Longitude: lon=78.53564

Example: http://comkits.com/processor.php?id=100&lat=17.23546&lon=78.53564

The http response shall contain the following data.

Device-Id, Registration Status (0-Failure, 1-Success)

The http response shall contain the following data:

Load Level.

HTTP Packet details(Contd)Details of Http packet from Rasp pi to the host server

After the device is registered and the ack is received from the server, the device is turned on. Then the device continuously sends http packet with the following details.

Device Id,

Load Level. (Currently the device is operating in which trigger level)

Reset Mode. (The mode to determine whether the device load has not being restored from semi full trigger level to full trigger level even after 2 hrs). Normally this field shall transmit 0, but when reset request is made it shall transmit 1, until the full trigger level is given.

This packet shall be transmitted every 30 seconds.

Example: http://comkits.com/processor.php?id=100&ld=25&rst=0

The trigger level shall be in percentage - 0% - No load, 25% - Minimum load, 50% Minimum load + geyser etc., 100% Full Load.

The http response shall contain the Load Level.

The parameters to be transmitted from the mobile device is as follows.

Preloaded device-id of the device, The Latitude and Longitude of the area.

The syntaxes used in the Http get packet is as follows:

Device-Id: id=10, Latitude: lat=17.23546, Longitude: lon=78.53564

Example: http://comkits.com/processor.php?id=100&lat=17.23546&lon=78.53564

The http response shall contain the following data:

Device-Id, Registration Status (0-Failure, 1-Success)

HTTP Packet details(Contd)Details of Http packet from Rasp pi to the host server

After the device is registered and the ack is received from the server, the device is turned on. Then the device continuously sends http packet with the following details.

Device Id.

Load Level. (Currently the device is operating in which trigger level)

Reset Mode. (The mode to determine whether the device load has not being restored from semi full trigger level to full trigger level even after 2 hrs). Normally this field shall transmit 0, but when reset request is made it shall transmit 1, until the full trigger level is given.

This packet shall be transmitted every 30 seconds.

Example: http://comkits.com/processor.php?id=100&ld=25&rst=0

The trigger level shall be in percentage.

0% - No load.

25% - Minimum load

50% Minimum load + geyser etc.

100% Full Load.

SLSS High Level Block Diagram

SLSS – Electrical Schematic

Practical Application The conventional electricity distribution board used in homes, offices, restaurants, clubs, shops and

other establishments using single or three phase supply are based on a simple distribution methodology. A single phase of a rated power capacity enters the consumer distribution box and is split into ”n” number of individual load circuits where the total load capacity of the main supply phase to the DB is distributed over “n” number of load circuits. At the entry of the DB there is a Master Circuit Breaker, followed by “n” number of circuit breakers of lesser capacity on the individual load circuit outlets from the DB box. The thumb rule in this load distribution scheme is as follows:

imaster circuit breaker = icircuit breaker (1) + icircuit breaker (2) + ………….. + icircuit breaker (n)

The imaster circuit breaker is the max. load demand for the specific consumer as allocated by the Utility company. I have shown a typical load outlay of 5.31 KW. The SLSS intelligent controller holds data on the maximum load allowable on the distribution board and is aware of the distribution of the allotted load over the various outlets available on the SLSS. The SLSS controller controls the total instantaneous load circuits coupled to the main power riser cable as shown in Figure 6 on page 7. On initialisation of the subscriber SLSS, it sets up a TCP/IP client connection over GSM-GPRS with the Utility company server. The access authorisation is granted by the Utility Control to the subscriber SLSS and the system activates the load circuit relays as shown in Figure 5, allowing the subscriber to use the electric gadgets at the particular subscriber location. Under normal conditions, the SLSS allows full loading enabling all the individual load relays on the distribution circuits in the SLSS. The subscriber is allowed to draw maximum power for using Lights, Fans, HVAC, Heaters, etc., at the home, office or any other category of installation. This is under normal conditions when the Load Demand is less than the Generation.

A model load restriction command

Market Potential of the project The application manages a perennial problem; the electric power crisis in many countries

and the problems of restricting consumer load demand and power outages.

As per an approximate estimation reached at from different sources for electricity consumers in a country like India with a population of something around 1.0 Billion people and that out of 150 Million electricity customers, some 20 Million does not have a metered connection. Billing is based on connected load. That encourages profligacy and wastage.

The electricity boards, are now opting for Automatic Meter Reading (AMR) devices based on GSM-GPRS connectivity. The paradigm of a successful reform would be to install the SLSS that would be an additional wonder gadget to the AMR. The SLSS would greatly restrict and reshape consumer load demand and reduce unwanted power outages that upset life in an urban/rural environment A modest market potential to start with would be 100 million consumers where the SLSS would serve to control and restructure Load Demand on Real Time basis and helping Utility companies offer an efficient load management with a better customer service.

The design technology is simple and straight forward. An electric distribution board (or panel board) is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure.

Approximate ExpensesThere isn’t any typical product of this type available in the market except for PLCC based Lighting ballasts which is only limited to controlling lighting loads at peak hours by dimming the same and in no way incorporate the functions as shown in the SLSS. The design and concept of the SLSS is unique. An approximate end customer price of the same should be around Rs 4000/- or even less for bulk quantities.

S.No

Item and Description Qty Amount in INR

 1 MS, DB Box Enclosure 1 2500.00

 2 MCU/MPU board 1 750.00

 3 Relay Driver Circuit 8 200.00

 4 Power Relays 8 1500.00

 5 Circuit Breakers 9 1500.00

 6 GSM/GPRS Module and Antenna

1 1500

 7 Wires Terminal and Strips 1 set 300

 8 Total Raw Material cost   6000

  Additional 10% manufacturing cost

  600

  MRP   6600

The future prospects of the design When power demand exceeds the generation capacity of the utility

company, the electricity system becomes unstable and a black out could result or a rolling blackout is performed by the utility company. To prevent this from happening, the electrical energy supplier can either increase the supply or decrease the customer’s demand. It takes more than 2 to 5 years to add power capacity by building new power stations and there might not be enough energy resources available to power electric generating stations. The only solution will therefore be to share the available capacity amongst customers through load shedding. Interruption simply means loss of productivity and the net losses are immense that affects the overall economy. The net results from power outages or rolling blackouts/load shedding are customer losses be it domestic or industrial.

The design tries to achieve a compromise between the two; when the ever increasing load demand from the customer side has surpassed the power generation and cannot be fully met by the utility company (the power plants run at 65-70% max. efficiency), the system dynamically adjusts the load to generation ratio to a 1:1. Its an adaptive system that is based on the utility companies assessment of the instantaneous load and load variation (di/dt) and systematically broadcasts control messages to the customer end SLSS’s to shed off load partially rather than totally and avoiding a total blackout / load shedding in customer areas. As shown below the system lowers the customer cost and the utility cost to achieve an optimum point A.

Figure 3: Adapted from the IEEE transactions on power system Vol.11,’No.2, May1996

Conclusion

Hence we see that this design has multiple benefits:

It is useful for the utility company to handle huge amount of load

It is useful to monitor the illegal loss of current

It could be useful to monitor any circuit problems much before complaint hence increasing customer reliability.

Thereby if this system is brought to use – the electricity will get a new face.