What is time current curve?
What is time current curve?
A time current curve (TCC) plots the interrupting time of an overcurrent device based on a given current level. These curves are provided by the manufacturers of electrical overcurrent interrupting devices such as fuses and circuit breakers.
WHAT IS curve in relay?
In electromechanical relays the curve is set by means of a dial which is why the setting is referred to as the “time dial setting” or TDS. In some relays, a Time Dial Multipler is used instead of Time Dial setting but their functions are similar.
How do you read time current characteristics curves?
To determine how long a breaker will take to trip at a given current, find the level of current on the bottom of the graph. Draw a vertical line to the point where it intersects the curve. Then draw a horizontal line to the left side of the graph and find the time to trip.
What is coordination time interval for relay?
If electromechanical relays are used, the coordination time interval recommended by IEEE 242-2001: IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (IEEE Buff Book) is between 0.3 and 0.4 second.
What are the various time current characteristics available for an overcurrent relay?
1) Operates in a definite time when current exceeds its Pick-up value. 2) Its operation criterion is only current magnitude. 3) Operating time is constant. 4) There is no intentional time delay.
What is IEC curve?
IEC 60255 IDMT Curves Inverse Definite Minimum Time (IDMT) curves are used in both mechanical and electronic protection devices. These curves define the amount of time which should pass at a given current, before initiating an action, usually the tripping of a circuit breaker.
How do you calculate the operating time of a relay?
Operating Time of Relay for Extreme Inverse Curve (t) =80/ ((PSM)2 -1). Operating Time of Relay for Long Time Inverse Curve (t) =120 / ((PSM) -1). Operating Time of Relay for Normal Inverse Curve (t) =0.14 / ((PSM) 0.02 -1). Operating Time of Previous upstream Relay = Actual operating Time of Relay+ Total Grading Time.
How do you plot TCC?
Plotting a TCC Curve from a One-Line
- Select only one item by clicking on the item.
- Select more than one item by holding down the CTRL key and selecting items individually, clicking the items that you would like to plot.
- Drag the mouse to form a box around the items you would like to plot.
What is a time-current characteristic?
A time-current characteristic curve, for any specified fuse, is displayed as a continuous line representing the average melting time in seconds for a range of overcurrent conditions. The melting time is considered nominal unless noted otherwise.
What is the minimum time coordinating interval between static relays?
0.12 second
Static Relay – Low Voltage Breaker coordination requires a minimum 0.12 second time margin between the curves.
How do you calculate operating relay time?
https://www.youtube.com/watch?v=8ZjqsoiG-nc
