Load Flow Study
Load flow studies are performed to determine the steady-state operation of an electric power system. It is one of the most important aspects of power system planning and operation and is used to determine the voltages, currents, and real &reactive power flows in a system under a given load conditions.
- Plan ahead and account for various hypothetical situations. For example, if a line/cable is be taken off line for maintenance, can the remaining lines/cables in the system handle the required loads without exceeding their rated values.
- Identify the need for additional generation, capacitive, or inductive VAR support, or the placement of capacitors and/or reactors to maintain system voltages within specified limits.
- Identify the losses in each branch and total system power losses.
- Necessary for planning, economic scheduling, and control of an existing system as well as planning its future expansion.
Short Circuit Study
Short circuit study is an accidental electrical contact between two or more conductors providing the lowest resistance path to flow current. It is also one of the most important aspects of designing power distribution systems.
Short circuit studies provide magnitude of the currents and voltages on a power system during fault conditions. This information is required to design an adequate protective relaying system and to determine interrupting requirements for circuit breakers at each switching location.
Short circuit studies used to determine any or all of the following:
- Selection of switchgear ratings
- Verify protective device close and latch capability
- Verify protective device interrupting capability
- Protect equipment from large mechanical forces
- I2t protection for equipment (thermal stress)
- Selecting ratings or settings for relay coordination
Motor Starting Analysis
Motor starting studies can help in the selection of best method of starting, the proper motor design, and the proper system design for minimizing the impact of the motor starting.
Motor starting analysis identifies the expected voltage dip and acceleration time for a motor and the effects of motor starting on a system.
The starting torque varies directly as the square of the applied voltage. Excessive starting current results in drop in terminal voltage and may result in the following:
- Failure of motor starting due to low starting torques.
- Unnecessary operation of under voltage relays.
- Stalling of other running motors connected to the network.
- Voltage dips at the power sources and consequent flicker in the lighting system.
Harmonic studies are performed to determine harmonic distortion levels within a facility and to determine if harmonic voltages and currents areat acceptable levels.
Harmonic current and voltage levels determined by simulation and evaluated with respect to recommended limits, such as those presented in IEEE Std. 519. If harmonic distortion levels are not within the acceptable limits the impact of harmonic filters is evaluated.
Harmonic studies are important for the following:
- Avoids damage due to excessive harmonic currents in transformers and capacitor banks.
- Ensures sensitive electronic equipment will not malfunction due to excessive harmonic voltage distortion.
- Satisfies the utility’s voltage and current harmonic distortion requirements.