This document describes the utilization of some new features offered by lEC 61850, Communication Networks and Systems in Substations. In particular, thepaper looks at how horizontal communication, commonly known as GOOSE communication, between protection and control devices can be used to improve the reliability and performance of the system. Besides describing generic improvements in capacity, performance and reliability, the paper presents a practical GOOSE application, i.e. blocking based busbar protection.
The protection of distribution networks is facing new challenges from an increasing amount of distributed generation (DG). Even though current technology provides satisfactory solutions to manage this new situation, loss-ofmains protection (LOM) is still considered problematic. The solution proposed in this paper focuses on the use of a line differential protection relay. It inherently contains a suitable communication channel and provides absolutely selective protection for the feeder. Furthermore, it prevents the feeder relays from false tripping for faults on the neighboring feeder. The present trend in protection communication points towards the use of fibre optics. For line differential protection, this means a fast and high-capacity communication link which enables the implementation of many advanced protection functions. In addition, a solid foundation for such a communication link is offered by the new IEC 61850 standard and Ethernet technologies. The basic functionality of the line differential protection enables the operation of both the feeder protection and the DG protection for any fault on the feeder. Furthermore, basic LOM protection methods can be applied as backup protection for failures on the communication link.
Modem urban power distribution networks are gradually developing from a radial-type topology towards ring-type and even mesh-type topologies. There are many drivers behind this development, one significant being the need to increase the reliability and availability of networks. From the network protection point of view the ongoing development poses new challenges for the prevailing protection philosophies and the protection relaying of today. Varying fault current conditions, magnitudes and contributions from several fault current sources represent challenges that are difficult to resolve with conventional overcurrent protection relaying. One solution to this problem is to introduce unit type protection schemes utilizing the differential current protection principle. Communicating multifunction line differential relays offer basic in-zone unit protection, and local and remote back-up overcurrent protection for the downstream power system, and dedicated earth-fault protection for enhanced line to ground fault sensitivity. The IEC 61850 standards combined with Ethernet communication technology already caters for new possibilities using horizontal communication within a substation. The suggested approach can also be extended to inter-substation communication and used in conjunction with line differential protection. The protection communication channel between the two line ends can also be used for transferring additional information between the substations, such as information related to other protection schemes or primary equipment interlockings or for enhancing performance of the unit protection under certain switching conditions.
This paper describes protection structures in MV networks, mainly the connection of instrument transformers (both inductive and electronic) and the measuring equipment used to analyze their signals. It summarizes the current situation and explains the ways in which this structure could be optimized and the design of it components simplified. Practical hints for such optimization are explained and examples are given. This paper also compares widely used protection schemes using classical inductive CTs/VTs with modern solutions offered by electronic CTs or VTs with extended performance.
Abstract. The study investigated the effect of a diet containing either a polyol mixture (polyol group) or molasses (molasses group) on the lactoperoxidase (LP) and thiocyanate (SCN ) content of milk and the udder health of dairy cows during a 12 week trial period. The control group received no extra carbohydrate feed.On the basis of the weekly milk samples from all test animals the polyol group had on an average the highest LP content (17.8 /ig/ml), the lowest SCN content (0.87 mg/1), and the lowest somatic cell count (152 000 cells/ml). The mean values for the molasses group were; LP: 12.6 SCN ; 1.01 mg/ml and cell count: 626 000 cells/ml. The same values for the control group were 11,7 fj g/ml, 0.91 mg/1 and 285 000 cells/ml, respectively.The polyol group yielded milk with an average of 51.5 % more lactoperoxidase daily than the molasses group, and 42.5 % more than the control group. These differences were, however, not found to derive from the different carbohydrate diet, because no significant change in the LP level in any group occurred during the test feeding. The On the basis of cell content and the occurrence of mastitis cases, the polyol group had the best and the molasses group the worst udder health.The possible effect of the LP/SCN /H 2020 2 antimicrobial system on mastitis resistance is evaluated.
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