The document outlines the operational objectives and controls of a power system, emphasizing the need for continual matching of load demand, reliability, and low-cost energy with minimal environmental impact. It discusses the hierarchical structure of control, the importance of coordination among various control areas, and the ownership dynamics of generation, transmission, and distribution systems. Additionally, it describes operational states of the system ranging from normal to emergency, detailing the necessary control actions for each state.

1. POWER SYSTEM
CONTROLS

2. OPERATIONAL OBJECTIVES
• Continual matching of load demand
• Certain level of reliability and
quality
• Electrical energy at low cost with a
low environmental impact

3. HIERARCHY OF CONTROLS
• Well defined hierarchy of controls, automatic/manual
• Generators have a wide array of automatic feedback control
systems
• Most of the controllers are decentralized
• Some decentralized controllers need system-wide coordination
• Reference values: closed-loop controllers/system operators
/energy control center

4. • A large power system may consist of autonomous control areas,
controlled independently
• Exchange pre-decided amounts of power with other areas through
interconnecting tie lines or DC links.
• However, during transients and abnormal conditions, they are
expected to act in co-ordination with each other.

6. OWNERSHIP AND CO-ORDINATION
• Scheduling of references may have economic and technical
consequences
• Ownership of generation, transmission and distribution systems
can be different and hence there may be multiple control center
obeying a certain hierarchy with a strictly defined authority.
Ownership of power system components is an important issue in
grid co-ordination.
• A typical power system consists of several "control areas". They
have an obligation to serve customers in their respective areas and
have complete authority over all activities in generation,
transmission and distribution in their domain of operation
("vertically integrated utilities").

7. • Inter-state and some other major transmission links may be owned
by an independent entity
• functions and ownership of the vertical integrated utilities are
divided by forming separate companies
• Overall operational co-ordination in an area is done by a load
dispatch center.
• Inter-area exchanges are coordinated by a central load dispatch
center.
• No part of an interconnected grid is totally independent of another.
All entities are required to co-operate to run a grid smoothly.

8. POWER NETWORK
• Transmission system: (i) all major generating stations and main
load centers, (ii) voltage levels (typically, 230 kV and above).
• Sub-transmission system: (i)transmits the transmission
substations to the distribution substations, (ii)Large industrial
customers
• Distribution system: (i) power to the individual customers,
(ii)between 4.0 kV and 34.5 kV

10. OPERATING STATES AND
NATURE OF CONTROL ACTIONS
• Is the demanded load being met?
• Are all equipment within their
current and voltage limits?
• Can the system withstand stresses
due a possible contingency (leading
to a loss of equipment)?

11. OPERATIONAL STATES
• Normal state: all system variables are within the normal range
• Alert state: security level falls below a certain limit of adequacy
because of a disturbance; generation shifting (security dispatch) ,
Increased reserve
• Emergency state: severe disturbance; fault clearing, generation
tripping, load curtailment
• In extremis: cascading outages; load shedding and controlled
system separation
• Restorative state: control action is being taken to reconnect all
the facilities and to restore system load.