James Stoupis

Demand Response Architecture: Integration into the Distribution Management System

Demand Response (DR) refers to actions taken by the utility to respond to a shortage of supply for a short duration of time in the future. DR is one of the enablers of the Smart Grid paradigm as it promotes interaction and responsiveness of the customers and changes the grid from a vertically integrated structure to one that is affected by the behavior of the demand side. In Principle, it is possible to perform DR at the substation level for the customers connected to the feeders downstream or at the demand response service provider (aggregator) for the customers under its territory. This would allow for an area based solution driven mostly by the financial aspects as well as terms and conditions of the mutual agreements between the individual customers and the utility. However, as the penetration of DR increases, incorporating the network model into the DR analysis algorithm becomes necessary. This ensures the proper performance of the DR process and achieves peripheral objectives in addition to achieving the target demand reduction. The added value to the DR algorithm by incorporating the model of the distribution network can only be realized if the engine is developed as an integrated function of the Distribution Management System (DMS) at the network control center level. This paper focuses on the demand response architecture implemented at the DMS level and discusses some practical considerations associated with this approach

Communication protocols and networks for power systems-current status and future trends

Minimizing implementation time and manual configuration, as well as straightforward upgradability are the key requirements of efficient substation automation systems. For larger utilities this often necessitates achieving interoperability between different devices from multiple vendors. Since the early 1990s it was noticed that the speed of advances in communication technology seemed to overpass its power system counterpart, which called for more adaptability by substation automation systems and higher independence from the underlying communication technology. The natural shift in the industry from proprietary communication protocols to open access standards was therefore further accelerated and was directed towards more advanced solutions that provide an interoperable and future proof environment. In order to be able to respond to these concerns, IEC 61850 was proposed as a future proof, adaptable communication protocol, capable of providing interoperability in a multi-vendor environment and with a highly advanced object oriented modeling structure. The migration from legacy protocols and de facto standards such as Modbus, DNP3, and IEC 60870-5 has already started and it seems likely that it will continue at a steady pace in the future. In addition to the efforts to provide an advanced solution for substation automation systems, there is also a need for extending the “automation” benefits to beyond the substations either downstream, at the feeder level or upstream, at a higher level of network management. The objective of this paper is to provide an overview of the current status of communication networks for substations using IEC 61850, and also discuss the possible future trends for extending the scope of the standard and using its capabilities for other applications within the distribution system.

Short-term load forecasting based capacity check for automated power restoration of electric distribution networks

This paper concerns power restoration control in an electric distribution network after a permanent fault. It describes a process for online estimation of loads in a network, which further enables determination of the pre-fault load. The pre-fault load is used to adjust short-term forecasting based load profiles, which are then used in capacity check algorithm of the power restoration controller to determine a backfeed that is valid up to several hours subsequent to the restoration. The paper also introduces a concept of source capacity constraint estimator that resides on Distribution Management System (DMS), with a virtual IED interface that provides up-to-date and accurate information of source capacity limits to the restoration controller. The methodology as proposed in the paper is validated using a laboratory demonstration network setup.

Applications of IEC 61850 in distribution automation

Distribution Automation (DA) is viewed as an integral component of the Smart Grid paradigm. It facilitates the employment of computer technology and communication infrastructure to advance management and operation of the distribution network from a semi-automated approach towards a fully automated one. SCADA systems, advanced sensors, and electronic controllers are integrated into the DA system in order to achieve the desired performance and reliability at the distribution network. Interoperability of all the components participating in the DA system requires communication standards covering not only the devices in the substation, but all the components from the substation to the point of interface with the end consumers. While the IEC 61850 standard was originally addressing applications and communications within the substation, recent work is undergone for extending it beyond the substation fence. With its object oriented structure, IEC 61850 can provide comprehensive and accurate information models for various components of distribution automation systems, while providing an efficient solution for this naturally multi-vendor environment. This paper provides some concrete examples on how IEC 61850 can be employed in the context of distribution automation applications, and what measures need to be taken to enable it to efficiently respond to some of the emerging technologies in DA systems.

Field investigation and analysis of incipient faults leading to a catastrophic failure in an underground distribution feeder

This paper deals with the subject of incipient faults in underground distribution systems and their progression over time leading to an eventual permanent failure. Field data recorded from an underground distribution feeder were analyzed in both time and frequency domain to identify the symptom parameters and characterize the observed incipient behavior. This exploratory data analysis sheds additional light on the progressive characteristics and nature of these self-clearing faults and advances the fundamental knowledge in an effort to detect such pre-mature failures before developing into a full-blown fault.

Modeling distribution automation system components using IEC 61850

IEC 61850 was proposed as a standard protocol for communications within the substation. In its current edition, the standard does not cover communications outside the substation, either with the control center or with other substations, for instance for remote protection. However, during the recent years, there has been a general belief that some features of the standard can be efficiently utilized for applications outside the substation as well. With the advent of new monitoring and control technologies the idea of power system automation at the distribution system and feeder level is crossing new boundaries. In such applications, accessing the accurate data is a necessity. With its future-proof object oriented structure, IEC 61850 can provide comprehensive and accurate information models for various components of distribution automation systems. This paper provides some examples on how the standard can be employed for this purpose, and what measures need to be taken to enable it to efficiently respond to some of the emerging technologies in distribution automation systems.

Protection coordination in active distribution grids with IEC 61850

This paper presents an adaptive protection scheme developed for distribution networks that include large number of Distributed Energy Resources and are capable to dynamically change configuration, i.e. active in nature. The system is based on a centralized controller running the real-time analysis of the data received from the field Intelligent Electronic Devices and communicating with IEDs by means of IEC 61850 communications.

Graph theory-based feeder automation logic for low-end controller application

This paper presents a graph theory-based feeder automation logic that is applicable to the low-end feeder automation controller, including programmable logic controllers (PLCs) and intelligent electronic devices (IEDs). IEC 61131-3 standard PLC programming languages are used to implement the entire logic engine in SoftPLC programming environment. This logic engine can provide following functions required by the real-time feeder automation application: (1) a dynamic update of the system configuration and the load profile and (2) a generic logic for fault location detection, fault isolation, and power restoration after the occurrence of a permanent fault in the distribution network. The logic engine implemented using PLC languages enables the low-end controller to perform complex feeder automation functions and facilitates end users (usually field electrical engineers) to easily understand and customize the logic. In addition, the SoftPLC technique makes the logic engine development independent of any proprietary PLC or IED hardware. The proposed feeder automation logic is demonstrated by example distribution feeder systems.

A deterministic analysis method for back-feed power restoration of distribution networks

This paper presents a deterministic algorithm that identifies a back-feed restoration strategy to restore the out-of-service load due to fault isolation while ensuring that the post-restoration network has a valid configuration. The algorithm is based on the concepts of network tracing and it supports both single-path and multi-path restoration. In case the network components are too stressed and even the multi-path restoration cannot restore all the out-of-service loads, the algorithm tries to shed minimal load while restoring as many other loads as possible. Capability of the algorithm is demonstrated with a few back-feed restoration solution examples.

Distributed automation for back-feed network power restoration

Smart Grid refers to electric power systems that enhance grid reliability and efficiency by automatically anticipating and responding to system disturbances. To achieve smart grid at the power distribution system level, various automatic technologies have been attempted in the areas of system metering, protection, and control. Within these technologies, automated power restoration is an important part of the Smart Grid puzzle. This paper presents an on-line method for the automated power restoration application previously described. The developed method conducts an analysis to achieve back-feed power restoration, i.e., healthy load zones that have lost power will be restored through their boundary tie switching devices from neighboring sources, and no reconfiguration beyond the tie devices will be considered. The back-feed restoration should not overload any part of the back-feeding network.