The Year of the Pig is coming to an End and we are welcoming the Year of the Rat. As usual our company has rented the Shenzhen sports stadium for the annual Spring Festival Gala and Outstanding Staff Award Ceremony. Colleagues from CLOU subsidiaries all over China have been present for this event. The audience was more than 1,100 people. This year we've provided a live stream for all those who had not been able to attend.
All show acts have been performed by CLOU staff. The preparations started around three month ago. The colleagues have spend a lot of their free-time to create this amazing event.
Thanks for watching and Happy New Year. We'll be back after the break 🙂 If you like you can leave some Lunar New Year greetings in the comment box below.
This post deals only with the aspects related to energy metering.
Transient voltages are short time surges in the a.c. power supply. They typically last a few milliseconds and the voltage can reach several thousand volt. A transient is by definition shorter than half cycle.
Causes for transients
There are two major groups of transient voltages.
Power system switching transients
Power system switching transients can be separated into transients associated with:
major power system switching disturbances, like capacitor bank switching
minor local switching activity or load changes in the power distribution system
resonating thyristors circuits
arcing faults to the grounding system
direct lightning stroke
induction due to an indirect lightning stroke
nearby lightning-to-earth discharge
Energy meters can not detect a voltage transient. The event is too short. Most power quality analyzers are designed to capture surges in voltage. The energy meters are protected to surge effects according to IEC61000-4-5. For certain regions additional external arresters can be added during meter installation.
A voltage swell is a surge (increase) of voltage above 110 % of the rms magnitude in your power grid. The duration can be between ½ cycle and one minute. (EN 50160) Note that not all smart meters have a power quality log. As us or your energy meter vendor.
events below ½ cycle are transients (not recorded)
events from ½ cycle to 30 cycles are instantaneous swells
events from 30 cycles to 3 seconds are momentary swells
events from 3 seconds to one minute are temporary swells
above one minute it's over-voltage (different event)
The graphics shows a five cycle voltage swell, coming from a large load has been turned OFF.
What is the cause for voltage swells?
sudden switching OFF of a big consumer (e.g. large electro-motor)
a change in the ground reference in floating or unearthed phases
Voltage swell event logging
A voltage dip event consists of:
magnitude the maximum measured instantaneous voltage in any phase during voltage swell condition
The magnitude percentage (threshold) and the duration can be configured in the settings. Energy meters have a typical interval time of 500 ms to retrieve the instantaneous voltage. When the voltage magnitude is set to 110% rms, the power quality event log will be full too fast. So choose a higher value to get reasonable benefit from the event log. If you don't mind to become annoyed from alert messages, you can also use an additional push event for voltage swell:)
The event starts when the instantaneous voltage rises above the threshold for the given duration. The event ends when the voltage drops 2 % below the threshold. (We are operating with a 2% hysteresis).
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