Peter Sutherland

Presentations:

Industrial Power System Grounding

Proper grounding is essential for the safe and reliable operation of electric power systems. There are several areas of grounding which must be considered: system grounding, equipment grounding, static and lightning protection grounding. System grounding is grounding of the electrical distribution system considered downstream of a transformer or generator. There are several types of system grounding: ungrounded, solidly grounded, high and low resistance grounded, inductive and resonant grounding. System grounding must be coupled to ground fault protection systems. Equipment grounding is grounding of the metal frames of equipment such as switchgear, panelboards, motors and generators. This routes any ground fault currents to back to the source. Static charges can accumulate on conductive parts which should be discharged. Lightning strikes can result in large currents which must be safely led to ground.

Commissioning & Periodic Maintenance of Microprocessor Based Protection Relay in Industrial Facilities

The first relays were Electromechanical (EM): machines with moving parts actuated by coils connected to current and voltage sources. These required regular testing, adjustments and maintenance to ensure continued functioning. Relays contained bearings, springs, fixed and movable contacts, rotating disks, air gaps, permanent magnets and other components. Static Relays containing analog and digital discrete electronic components and small ICs similarly required testing and adjustments but less maintenance. Relays have become Intelligent Electronic Devices (IEDs) in power systems, doing much more than protection. Microprocessor Relays use Digital Signal Processing and Protection Algorithms have no adjustments. What does test and maintenance mean, and when is it required?

Motor Starting Studies

Motor Starting Studies (based on IEEE Std 3002.7™-2018) This presentation will cover the calculations necessary for analyzing the starting of a large induction or synchronous motor on a three-phase power system. A motor which is large in proportion to the power system which feeds it, in terms of the capabilities of generators, transformers, and feeders, will impose stresses on the system such as over-currents and under-voltages. Depending upon the characteristics of the motor, it may stall and not accelerate, or may accelerate too slowly and overheat, causing damage to the motor. A motor starting study will include a time-domain analysis of the motor acceleration based upon its published curves, in conjunction with load-flow and perhaps transient stability analysis of the supplying power system. A motor starting study may also be needed to properly determine protection settings for the motor protective relay.

Stability Studies for Industrial Power Systems

A stability analysis provides the time response of a system of rotating machines due to a system disturbance. A stability analysis for a system with local generation is required in several circumstances. Such as: Large motors pull out of step or stall on impact loads. New generation is added to the system. A loss of generation causes a system shutdown. Heavy loading of the generator causes it to pull out of step. A short circuit is not cleared promptly. A tie breaker or line opening event causes system separation.

The information supplied by a stability study includes: Whether the system relaying will clear a fault before a generator or synchronous motor pulls out of step. The response of the system voltage after a disturbance such as faults or motor starting. The response of the system frequency due to loss of a utility tie for calculating underfrequency relay settings. The amount of load to be shed after an underfrequency relay operation. The generator’s ability to pick up or reject load. Whether motors and generators will remain in step when major ties are opened. The loading and excitation levels of generators to improve the stability limit.