UNIT-V(operation of modern power systems)

1. Topic: Utility functions

An electric utility is a company in the electric power industry (often a public utility) that
engages in electricity generation and distribution of electricity for sale generally in a
regulated market. Power & Utilities includes electricity power generation, transmission and
distribution of a public service (Utilities), usually in the form of electricity, water and heating
(gas), but depending on the jurisdiction, can include telecommunications and broadband
services also. The major goals of an electrical utility can be broadly categorized into three: -

Control the long-term costs of the electric system: The regulatory framework should
promote a broad range of resources to increase the ratio of average to peak electric load,
helping to right-size the electric system to customer’s needs.
 Give customers more energy choices: The regulatory framework should allow
customers to use emerging technologies and commercial arrangements to manage
their energy production and use.
 Build a flexible grid to integrate more clean energy generation: The regulatory
framework should promote the flexibility needed to allow the electric grid to
incorporate an increasing proportion of variable clean energy through use of demand
response and energy storage, for example.
Regarding the utility “Data Connectivity, i.e. telecommunications and broadband services” it
can be stated that “the electric system of the 21st century will depend on operation of data
networks to allow the utility to gain visibility and control of the electric system. Many of the
functions associated with operation of a data network are outside the electric utility’s
traditional area of operations and include strategically important, but not capital intensive,
software and service components. Taken together, these considerations may guide the inquiry
into what the utility of the 21st century should do, how it should earn revenue, and what kind
of metrics should shape its operation.

The potential functions of a twenty-first century electric utility may include:

 Reliability services, such as pole and line maintenance, circuit reconfiguration,

supplemental power supply, undergrounding, power factor correction, distribution
system engineering and voltage variation optimization.
 Connectivity services including operation of the communications backbone to support
distribution line automation and to enable potential advanced metering functionality.
 Network integration services, such as scheduling, multi-directional power flow and
management services, storage-based power “loan” services, electric vehicle charging
services, and the necessary distribution system planning and data analysis for load,
 voltage and hosting capacity. 
 Transaction management services, such as aggregation, clearing and settlement
among parties, integration of distributed energy resources and metering customers.
 Customer engagement services, such as home energy optimization, appliance
automation, intelligent load management, backup energy services including energy
storage, energy efficiency program delivery, customer support, low-income
engagement and electric vehicle education. 
Many of these functions are so connected with one another that they are best
undertaken by a single enterprise. However, there may be functions that could be
undertaken separately or which the electric utility may not be optimally organized to
perform.

2. Topic: Power Exchange (PX)

A power exchange may refer to the entity that operates an electricity market at which
electricity is traded. PX is a trading center where utilities, power marketers, and other
electricity suppliers submit price and quantity bids to sell energy or services, and potential
customers submit offers to purchase energy or services. Key points of a power exchange
include:

• Facility for trading of electricity: This market place permits different participants to sell and
buy energy and other services in a competitive way based on quantity bids and prices.
Participants include utilities, power marketers, brokers, load aggregators, retailers, large
industrial customers and co generators · PX is a new independent, non government and non
profit entity which accepts schedules for loads and generation resources.

• Foster the development of competition: It provides a competitive market place by running

an electronic auction where market participants buy and sell electricity and may do business
quickly and easily. Through an electronic auction, PX establishes an MCP (marginal cost
price) for each hour of the following day for trades between buyers (demands) and
sellers(suppliers).

• Transparency: It submits balanced demand and supply schedules for successful bidders to
ISO(Independent System Operator) and performs settlement functions with ISO as well as
PX participants such as UDCs (Utility Distribution Companies), marketers, aggregators etc
· It also submits ancillary service bids to ISO for maintaining system reliability , adjustment
bids( may be used to relieve or eliminate congestion on transmission grid) · PX guarantees
anequal and non discriminatory access and competitive opportunities to all participants.
 • Liquidity: In this market place PX does not deal with small consumers. PX manages
settlement and credit arrangements for scheduling and balancing of loads and generation
resources.

3. Electricity Market Models

Market participants can avoid congestion charge by forming a pool and entering into financial
contracts. A pool model with locational market prices defined for every node is often
considered as an ideal market model as the nodal prices perfectly reflect all costs of
supplying electricity at given nodes and, manage congestion at the same time.

Two main technical features determine the complexity of such models: the product
‘‘electricity’’ which cannot be stored and its transportation that requires a physical link
(transmission lines). Proper market models, in most cases, must deal with imperfectly
competitive markets, which are much more complex to represent. Some market models used
in the power industry are as follows:
3.1 Vertical Market Model
The electric power industry has over the years been dominated by large utilities that had an
overall authority over all activities in generation, transmission and distribution of power
within its domain of operation. Such utilities have often been referred to as vertically
integrated utilities. Such utilities served as the only electricity provider in a region and were
obliged to provide electricity to everyone in the region. The typical structure of a vertically
integrated electric utility is shown in figure 5.1 below. In the figure, the money flow is
unidirectional, i.e. from the consumer to the electric company. Similarly, the information flow
exists only between the generators and the transmission systems. In vertically integrated
utilities, it was often difficult to segregate the costs involved in generation, transmission or
distribution. So, the utilities often charged their customers an average tariff rate depending on
their aggregated cost during a period.
 Figure 5.1: Vertically integrated market model

Demerits: -
 Generally one firm, once with a franchise.
 Regulators approve what utilities build. This may or may not be the lowest cost investment,
and may or may not be technologically innovative.
 Traditional utility regulation accommodates the use of more debt, but limits innovation.
 Risk and return expectations will be relatively lower. This will affect what types of entities
hold ownership stakes.
 Reduced need for marketing and business development. Largely focused on providing onesize-
fits-all solutions for customers.

5.2 Wholesale Competition Model

This model is one step closer towards competition. There is an organized market in which the
generators can sell their energy at competitive rates. The market may be organized either by a separate
entity or may be run by the system operator itself. There is not much choice for the end user. The end
user is still affiliated to the Discom (Distribution company) or retailer working in that geographical
area of operation. The large customers or the bulk customers, so to say, are privileged to choose their
energy provider. However, the definition of bulk customer is a subjective matter and changes from
system to system.

This model, as shown in Figure 5.2, provides the choice of supplier to Discoms, along with competition
in generation. Implementation of this model requires open access to the transmission network. Also, a
wholesale spot market needs to be developed. Discoms can purchase energy for their customers either
from a wholesale market or through long term contracts with generators.

The customers within a service area still have no choice of supplier. They will be served by a Discom
in their area. With this model, the Discoms are under Universal Service Obligation (USO), as they
have monopoly over the customers. They own and operate the distribution wires. The transmission
network is owned and maintained either by government and/or private transmission companies.
System operators manage the centrally accomplished task of operation and control.
 Figure 5.2: Wholesale Competition Model

The model provides a competitive environment for generators because the wholesale price is
determined by the interaction between supply and demand. In contrast, the retail price of electrical
energy remains regulated because the small consumers still do not have a choice for their supplier. The
distribution companies are then exposed to vagaries of the wholesale price of the commodity. The
merits and demerits of this model are as follows:

Merits: -

 Choice of seller provided for Discoms and bulk consumers.

 The buyers and sellers can make forward contracts or buy from a wholesale marketplace.
 The price is decided by interaction between demand and supply. Hence, indicates truly
competitive price.

Demerits: -
 The end consumer still doesn't have a choice. It buys power from the affiliated Discom.
 Rates for end consumers are regulated rather than competitive.
 Discoms face competition at wholesale level, while their returns are regulated.
 Structural and institutional changes required at wholesale level.

5.3 Retail Competitive market

In this model, as shown in Figure 5.3, all customers have access to competing generators either directly
or through their choice of retailer. This would have complete separation of both generation and
retailing from the transport business at both transmission and distribution levels. Both, transmission
and distribution wires provide open access in this model. There would also be free entry for retailers.
In this model, retailing is a function that does not require the ownership of distribution wires, although,
the owner of distribution wires can also compete as a retailer.

This model is a multi-buyer, multi-seller model and the power pool in this model acts like an
auctioneer. It behaves like a single transporter, moving power to facilitate bilateral trading and this is
achieved through an integrated network of wires. In this pooling arrangement, there is a provision for
bidding into a spot market to facilitate merit order dispatch. The pool matches the supply and demand
and determines the spot price for each hour of the day. It collects money from purchasers and
distributes it to producers.

The advantage of this model over monopoly utilities is that competition is introduced in both wholesale
and retail areas of the system. This model is supposed to be a truly deregulated power market model.

The retail price is no longer regulated because small consumers can change their retailer for better
price options. This model is economically efficient as the price is set by interaction of demand and
supply. In wholesale competition model, with relatively few customers, all of them regulated Discoms,
a spot market can be preferable but not essential.

However, in retail competition model, spot markets become essential, since contractual arrangements
between customers and producers are carried out over a network owned by a third party. In retail
competition model, metering becomes a major problem. If the number of customers is increasing and
metering capability for all the customers is not sufficient, it may create logistical problem and provoke
disputes.
Figure 5.3: Retail Competition Model

Merits:

 Supposed to be 100% deregulated model.

 Every consumer has a choice of buying power.
 The price is decided by interaction of demand and supply. Hence, it is truly competitive price.
 There is no regulation in energy pricing.
Demerits:

 Need constitutional and structural changes at both, wholesale and retail level.
 Extremely complex settlement system due to large number of participants.
 Requirement of additional infrastructural support.

6. Topic: Demand side Management

Demand Side Management (DSM) is used to describe the actions of a utility, beyond the customer's
meter, with the objective of altering the end-use of electricity - whether it be to increase demand,
decrease it, shift it between high and low peak periods, or manage it when there are intermittent load
demands - in the overall interests of reducing utility costs. In other words, DSM is the implementation
of those measures that help the customers to use electricity more efficiently and in doing so reduce the
customers use and the utility costs.

DSM can be achieved through.

- Improving the efficiency of various end-uses through better housekeeping correcting energy
leakages, system conversion losses, etc

- Developing and promoting energy efficient technologies, and

- Demand management through adopting soft options like higher prices during peak hours,
concessional rates during off-peak hours seasonal tariffs, interruptible tariffs, etc.

DSM, in a wider definition, also includes options such as renewable energy systems, combined heat
and power systems, independent power purchase, etc, that utility to meet the customer's demand at the
lowest possible cost. Hence DSM can be achieved through energy efficiency by reducing energy

consumption on the one hand and on the other hand by managing the load demand itself. The first may
be achieved through awareness on use of energy efficient equipment on the part of consumer. Thus, it
leads to conservation of energy. However, the latter calls for reduction in power demand or shifting it
to off-peak hours. This can be achieved with utility providing incentive like time-of-use tariff giving
rebate during off-peak. Of course, utility has a leading role always through its actions that effect
quantity or pattern of energy consumption by the consumer through reduction of drawl during peak
period. This will in turn help the utility to reduce investment for generation vis-à-vis transmission and
distribution, as the case may be.
 7. Topic: Transmission pricing

Federal Energy Regulatory Commission (FERC) recognized that transmission grid is the key issue to
competition, and issued guidelines to price the transmission. The guidelines are summarized such that
the transmission pricing would:

 Meet traditional revenue requirements of transmission owners

 Reflect comparability: i.e. a transmission owner would charge itself on the same basis that it
would charge others for the same service.
 Promote economic efficiency. 
 Promote fairness.
 Be practical. 
 Even though transmission costs are small as compared to power production expenses and
represent a small percent of major investor owned utilities’ operating expenses, a transmission
system is the most important key to competition because it would provide price signals that can
create efficiencies in the power generation market.

Transmission pricing methods:

1. Contract Path Method

2. MW-Mile method

1. Contract Path Method: · It has been used between transacted parties to price transmission where
power flows are assumed to flow over a predefined path(s). · Despite its ease, this technique was

claimed be a bad implementation of true transmission pricing as power flows would very seldom
correspond to predefined paths. · Physically, electrons could flow in a network over parallel paths
owned several utilities that may not be on the contract path. · Parallel path flows refer to the
unscheduled transmission flows that occur on adjoining transmission systems when power is
transferred in an interconnected electrical system. · As a result, transmission owners may not be
compensated for the actual use of their facilities. · Added to parallel flows, the pancaking of
transmission rates is another shortcoming of this method. · Pancaking is when contract path crosses a
boundary defining transmission ownership, additional transmission charges would be added to a
transaction, which in turn might increase the price of the transaction. · In-efficient method

2. MW –Mile method: · Several ISOs are using a MW-Mile approach to price transmission. · The
MW-Mile rate is basically based on the distance between transacted parties (from the generating source
to the load) and flow in each line resulted from the transaction. · This approach takes into account
parallel power flows and eliminates the previous problem that transmission owners were not
compensated for using their facilities. · This approach does not give credit for counter-flows on
transmission lines. · The method is complicated because every change in transmission lines or
transmission equipment requires a recalculation of flows and charges in all lines.
8. Topic: Ancillary Services

Ancillary services are defined as services which are required to support the transmission of capacity
and energy from resources to loads while keeping a reliable operation of the transmission system of a
transmission provider in accordance with Good utility practice.

Ancillary services are the specialty services and functions provided by the electric grid that facilitate
and support the continuous flow of electricity so that supply will continually meet demand. The term
ancillary services is used to refer to a variety of operations beyond generation and transmission that
are required to maintain grid stability and security. These services generally include, frequency control,
spinning reserves and operating reserves. Traditionally ancillary services have been provided by
generators, however, the integration of intermittent generation and the development of smart grid
technologies have prompted a shift in the equipment that can be used to provide ancillary services.

A large number of activities on the interconnected grid can be termed as ancillary services. However,
in order to remove this large discrepancy, the North American Electric Reliability Council (NREC)

along with Electric Power Research Institute (EPRI) has identified 12 functions as ancillary services.
These are:

1. Regulation: The use of generation or load to maintain minute-to-minute generation-load balance

within the control area.
2. Load Following: This service refers to load-generation balance towards end of a scheduling
period.
3. Energy Imbalance: The use of generation to meet the hour-to-hour and daily variations in load.
4. Operating Reserve (Spinning): The provision of unloaded generating capacity that is
synchronized to the grid and can immediately respond to correct for generation-load imbalances,
caused by generation and /or transmission outages and that is fully available for several minutes.
5. Operating Reserve (Supplemental): The provision of generating capacity and curtailable load to
correct for generation-load imbalances, caused by generation and /or transmission outages, and
that is fully available for several minutes. However, unlike spinning reserves, supplemental reserve
is not required to respond immediately.
6. Backup Supply: This service consists of supply guarantee contracted by generators with other
generators or with electrical systems, to ensure they are able to supply their consumers in case of
scheduled or unscheduled unavailability.
7. System Control: This activity can be compared with the functions of the brain in the human body.
System control is all about control area operator functions that schedule generation and transactions
 and control generation in real time to maintain generation load balance.
8. Dynamic Scheduling: It includes real-time metering, tele-metering along with computer software
and hardware to virtually transfer some or all of generator’s output or a customer’s load from one
control area to another.
9. Reactive Power and Voltage Control Support: The injection or absorption of reactive power
from generators or capacitors to maintain system voltages within required ranges.
10. Real Power Transmission Losses: This service is necessary to compensate for the difference
existing between energy supplied to the network by the generator and the energy taken from the
network by the consumer.
11. Network Stability Services from Generation Sources: Maintenance and use of special
equipment (e.g., PSS, dynamic braking resistances) to maintain secure transmission system.

12. System Black Start Capability: The ability of generating unit to proceed from a shutdown
condition to an operating condition without assistance from the grid and then to energize the grid
to help other units start after a blackout occurs.

It should be noted that identification and definition of a particular ancillary service is system
dependent. There is no global definition of a particular ancillary service that is applicable in all
systems.