- IEC 60255-3
- What is meant by B, C, D, K and Z curves in MCBs?
- Time/Current curves
- Electromechanical Relays
Electromechanical relays have been the traditional backbone of electrical protection systems. While over recent years these have been replaced by microprocessor based numerical devices, there are still many older electromechanical relays in service. Mechanical relays developed in the s were the first form of electrical protection. While still being reliable and widely used these were superseded by static relays in the early s. Static relays have no moving parts hence the name and operated on the basis of analogue circuitry. More recently static relays have been superseded by first digital relays and now numerical microprocessor based devices. Each characteristic can be calculated from:. Relay characteristics are sometimes classified according to the tripping time at 10 times the setting current i. Tripping times for the various relays are:. These are given by:. An Amp breaker protected by relay with Standard Inverse characteristic. The relay pick-up current value is set at 0. What will be the tripping time? If you have the 3sec relay's trip curve, you can just multiply the time with 1. That is the time for the 1. The company history has changed over the last few years. Recently the company has now been acquired by Areva. If current transformers are connected in a residual circuit, saturation of one or more of the transformers during transient events may result in large spill currents. Particularly with high impedance relays, this may cause the the relay to falsely operate. To achieve stability under these conditions, stabilising resistor resistors are added to increase the minimum relay operating voltage. Note: The power rating of the stabilising resistor should be chosen taking into consideration the expected magnitude and duration of the current through the resistor. Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author. Can you please answer A ACB is set at 0. Joby, I've added an example to the post using your values and also a new calculation tool see the example for the link. Let me know if you see anything wrong. Hello Mr. Im having some trouble to understand the exact terms i have to put in the form. If i have a relay with A Iprimary and 1 A as Isecondary, and i establish a pickup I of 7A 7 times my In thats is 1Aand then i inject 8 A trough the relay in the secondary. What shall i put in the form? If i do so i get 5, 24 sec of trip, and im doing the test physically and the machine indicates 2,01 sec. So im putting something wrong in the form.
What is meant by B, C, D, K and Z curves in MCBs?
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Page of Go. Page - Figure P used to protect an autot Page Page - Example 3: Autotransformer with Unloaded Page - Figure Unloaded delta - current dist Page - Setting Guidelines for Short-Interconnec Page - Figure Single bus differential prote Page - Figure Shunt Reactor single line dia Page - Setting Guidelines for Reference Vector Page - Figure Automatic selection of distu Page - Figure Configuration file extractio Page - Performance of Frequency Protection Func Page - Performance of Monitoring and Control Fu GE Energy Connections. Table of Contents. Micom p40 agile single br eaker multi-end current differential ied non distance pages. Feeder protection system feeder protection and control pages. L90 line current differential system ur series pages. Page 4 Contents P64x 4. Page 9 P64x Contents 2. Page 10 Contents P64x 4. Page 12 Contents P64x 6. Page 17 P64x Contents Page 20 Differential protection blocking mechanisms Figure Triple slope characteristic Figure P used to protect a two winding transformer Figure P used to protect an autotransformer with loaded delta winding Figure P used to protect an autotransformer with unloaded delta winding Figure Unloaded delta — The level at which this manual is written assumes that you are already familiar with protection engineering and have experience in this discipline. The description of principles and theory is limited to that which is necessary to understand the product. Page Nomenclature Some of these terms are well-known industry-specific terms while others may be special product- specific terms used by GE. The first instance of any acronym or term used in a particular chapter is explained.