Terence Hazel

All your eggs in one basket [back-up protection using multifunction relays]

Multifunction microprocessor-based relays are commonly used in modern installations due to the many advantages they offer, such as communications, measurements, simplified wiring, self monitoring, and reduced space requirements. A reliable protection scheme is very important in order to protect capital equipment and operating personnel and reduce down time by selectively clearing faults. Back-up protection is also normally provided to ensure the elimination of faults should the primary protection circuit fail. In this article, the authors show how the features of modern multifunction relays can be used to enhance back-up protection. To better understand why multifunction relays can improve back-up protection, it is necessary to first review what back-up protection is and how it has been implemented in the past. This review is based on the electrical distribution system typically found in large petrochemical installations.

Taking Power Distribution Under the Sea: Design, Manufacture, and Assembly of a Subsea Electrical Distribution System

Recently, the offshore industry has seen a clear trend for production facilities to be installed on the seabed. The total electrical load will be up to the 100-MW range, and thus, high-voltage (HV) power distribution is required. Such a system is particularly beneficial in challenging environments, such as the deep sea and the Arctic, providing an efficient and economical subsea-to-beach solution that eliminates the need for a floating production unit. There are several advantages to installing process equipment close to the source of the product. Currently each item of process equipment is individually powered from the surface, which is reliable but very costly. Placing the electrical distribution system on the seabed drastically reduces the cost of the power supply and can be done without any reduction in reliability. Thus, the electrical power distribution will be located near the load center, which is a common practice for onshore designs.

Facilitating plant operation and maintenance using an electrical network monitoring and control system simulation tool

The use of simulators for training operators of electrical distribution systems is becoming more and more important. Modern industrial electrical distribution systems are very reliable and switching operations are not often performed. Mistakes can be very dangerous for personnel and equipment as well as being costly due to the production losses incurred. The authors describe the integration of a simulator into an electrical network monitoring and control system (ENMCS) in a chemical production facility in the south of France and how it is used to provide operator training as well as the preparation of switching operations. The addition of an ENMCS in an existing plant in commercial operation is also illustrated in this paper.

IEC medium-voltage circuit-breaker interrupting ratings-unstated short-circuit considerations

IEC medium-voltage circuit-breaker interrupting ratings are reviewed using typical petrochemical examples. This paper investigates the complexity of high-magnitude X/R ratios, and short-circuit current zero-axis crossings beyond the interrupting time of the standard circuit-breaker for generator applications. Guidelines are provided, enabling the engineer to correctly define the circuit-breakers and switchgear for these applications.

CT Saturation Calculations - Are they Applicable in the Modern World? - Part II, Proposed Responsibilities

Part I expressed concerns about using IEEE Standard C37.110-1996 (1+X/R) criteria for sizing current transformers (CTs) for feeder short-circuit conditions [1]. Part II introduces an overview of relay filter algorithms, and proposes responsibilities of the IEEE Power System Relay Committee (PSRC), operating company and engineering company electrical power engineers, CT manufacturers, switchgear manufacturers, and relay manufacturers to guarantee CT/relay system performance. International Electrotechnical Commission (IEC) responsibilities are also included.

Power Distribution for Arctic Subsea Tiebacks

Subsea tiebacks are becoming increasingly prevalent in oil and gas field developments. As the accessib ility of the production from wellheads becomes more difficult, the need for subsea compression and pumping increases. Compression and pumping require significant power which can be distributed and controlled from a HVSS (High-Voltage Subsea Substation). The viability of an Arctic field development will be de termined by the reliability of all elements in the tieback and in particular, the centralized subsea power distribution system.

Powering Subsea Processing Facilities of the Future

Subsea processing is going to increase dramatically over the next several years. A key component is a reliable power supply for the process loads. Located in a hostile and remote environment, the electrical distribution system will need to be designed according to the highest standards in power engineering ensuring dependable information for control and safe operation, and adaptability to changing operation conditions during the life of the field. A very important means of enhancing availability of the power supply is the possibility to do maintenance. For subsea applications this means the ability to locate where the fault has occurred and to be able to disconnect and retrieve the faulty equipment. This paper will describe how subsea power distribution can be achieved today based on known and proven technology. Equipment that has an excellent track record for surface processing facilities, installed in enclosures designed for the subsea environment and interconnected using cutting edge technology, will bring subsea processing facilities from the realm of fiction to reality. For more information about this publication please contact: sales@oceanworks.com

Never Take Safety for Granted: Safety As Main Design Criteria for All Electric Power Distribution Systems

Personal safety and protection of the environment are the main design criteria for all electric power distribution systems. The engineer responsible for power system design must take into account the loads to be supplied and available power sources to ensure the required system availability and robustness. The system must enable routine maintenance to be carried out to avoid a reduction in performance over time. Safety criteria must be integrated into the design process from the start as they will influence all choices that are made during the design process. A choice between a reliable system and a safe system has no meaning. The system must be reliable to supply the loads and must be safe.

Implementing back-up protection using microprocessor based multifunction relays

The use of microprocessor based multifunction relays is on the increase due to the advantages they offer such as communications, measurements, simplified wiring, and reduced space requirements. Since many protection functions are included in one device however, there has been some concern about providing adequate protection should a multifunction relay fail. A reliable protection scheme is very important in order to protect capital equipment and operating personnel, and reduce down time by selectively clearing faults. This paper analyses some of the different means that have been used to achieve satisfactory levels of back-up protection using microprocessor based multifunction protection relays featuring the protection functions normally provided in large petrochemical plants.

Industrial Power Systems Using Dry Low Emission Turbines

Gas turbines often provide the power necessary for the process at production sites. These power systems are much different from the utility grid. Being smaller, they are subject to large disturbances causing wide variations in turbine power over short periods of time. These power swings can have negative effects on some types of turbines designed to have low emission of nitrogen oxides. Such turbines use different firing methods at low and high values of power. The transition between these ranges and firing methods can lead to flameout. Turbines struggling to maintain power system stability at an industrial facility may succumb to the disturbance, resulting in a system collapse and loss of production. Regulations concerning emissions are becoming more severe, so this problem will become more challenging. Turbine firing techniques that allow low emissions for all values of output power are reviewed. The benefits this offers to the power system and the design of the power management system are also discussed. Using only one firing technique eliminates the risk of flameout and enhances power system availability. Another advantage of this firing technique is better parallel operation of turbines, particularly when machines have different ratings. Operating all turbines at the same relative power improves stability since all machines will react by the same amount during disturbances.