Sistema nga automatikong pangprotekta sa distribusyon nga may mataas nga presisyon nga PMU

Ang PMU distribution line protection automation system usa ka bag-ong sistema sa automatikong pagprotekta sa distribution line.

Para masolbar ang kasamtangan nga problema, partikular sa earth fault.

Basaha kini sa Distribution Network Synchronous Phasor Measurement-μPMU.

Ang PMU (phasor measurement unit) usa ka independiente nga device o module. Ang voltage/current sampling data adunay timestamp gikan sa BDS/GPS nga akurat hangtod sa US level.

Pangutana nga mga function:• Phasor: amplitude, phase Angle,• Frequency (f) ug Frequency Variation (△f/△t)

μPMU Hardware Architecture Block Diagram

Wide Area Measurement System (WAMS)
• Ang PMU measurements absolutong synchronized sa World
Standard Time (UTC)
• Wide-area measurement synchronization sa daghang PMUs
na-install sa lain-laing lugar
• Mathematical expression sa voltage/current signal:

Overhead Current Sensor i-WCS – Single Channel Current PMU

Solution alang sa problema sa distribution network nga gisubli sa distribution
network PMU ug ang wide area synchronous phasor measurement technology.

• Mataas nga precision ug mataas nga frequency
current acquisition
• Wide-area synchronized, power
induction
• Live installation, IP67 protection
• Suporta sa bi-directional power flow
o ring network operation
• 3G/4G/ 5G communication：
a. Periodically report each harmonic
b. Local events trigger the upload data
c. Remote call and test specific
moment data

• 1μs Wide-area synchronized
• 12.8kHz Sample frequency
• 60 min Wave record and playback
• 0.5 Measuring accuracy
• 3.5A Full function minimum operating
current

Cable Type Current Sensor RCMU – Multichannel Current PMU

RCMU - Underground cable
current sensor

• 1μs Wide-area synchronized
• 12.8kHz Sample frequency
• 0.5 Measuring accuracy
• 60 min Data Playback
• 3 current measuring
• Wireless/wired remote transmission

• Collect three-phase current, same as overhead
type principle, suitable for ring main unit,
switching station, substation.
• Wide area synchronous, induction power, or
24V/48V DC power supply
• Local fault decision algorithm based on current:
a. Short-circuit overcurrent
b. Zero sequence overcurrent
c. Asymmetric phase current
• Wave record called measurement, Support
distributed fault location
• Support bi-directional power flow or ring
network operation
• 3G/4G/5G or network communication

Bus Collecting Unit BDCU – Single/Multiple Voltage PMU

Indoor type
ug Outdoor type

• 220V AC/24V DC power supply• Fiber optic, wired, wireless
• IEC 60870-5- 101/104/DNP3• 300 current sensors can be accessedVoltage Acquisition：
• 1μs Wide-area synchronized
• 1.0 Measuring accuracy
• 12.8kHz Sampling frequency
• 60 min Wave record playback

Alang sa single-phase grounding fault nga may ground current
greater than 1A, ang detection ug positioning
accuracy is 100%, with 0 false positives
• Collect zero sequence voltage, start recording of
earth fault
• Collect and process the recording wave, and
determine the fault comprehensively
• Safe access to the main power distribution station
a. Used as the station grounding insulation monitoring
device
b. Used as an in-station grounding insulation
monitoring device
c. Do not rely on the master station to complete the
fault

The Composition of Intelligent Distribution Network Condition Monitoring
System Based on PMU Measurement

Distribution Network Usage Scenarios

Typical Use of PMU - Line Condition Assessment

Typical Use of PMU - Distributed Wave Recording

Ang recording data sa tanang monitoring points sa line ug station mao ang labeled sa absolute time sa
level of microsecond. Ang bisan unsang device makapuyde mag-trigger sa recording kon ang preset start conditions naabot. Provide a "snapshot" of the entire network based on the time callback of any event at any locationup to the recorded data of all sensors. It provides global data for detailed analysis of events and
facilitates process inversion, traceability, and early warning of abnormal state, etc.

Typical Use of PMU - Power Quality Monitoring

Ang sensor makakalkula ug report harmonics in real time. Based on the wide area synchronous
data, various power quality indexes such as three-phase unbalance, grid frequency and frequency
change rate can be calculated, and the pollution source load can be located accordingly.

Typical Use of PMU - Electricity Anti-stealing

According to the user's high-voltage side load data and current waveform, the load characteristics are
analyzed and identified, and the terminal user's electrical behavior is monitored, which can be used for
remote monitoring and diagnosis of the state of electrical equipment.

Typical Use of PMU: Fault Warning, Traceability and Process Inversion

Warning：
• 2017-10-30 12:15:39：081719, line 115, pole 1# 64#, phase A to ground
• 2017-10-30 12:15:39：093125 , line 117, pole 29#, phase B grounded short
circuit, peak flow exceeds 1000A
• 2017-10-30 12:15:39：115468 , Line 115, between poles 1# and 64#, phase A
and C short circuit, Peak current at pole 1# exceeds 5000A
Field feedback and fault process inversion:
• A car collision accident occurred at pole 52# on line 115
• The inspection found a burn mark in the cable cabinet somewhere behind the
pole 29# on line 117
• Speculating that phase A conductor of line 115 falls down the cross arm and
causes grounding, and the electric voltage of the non-fault phase increases,
which leads to the breakdown of the insulation weak point phase B behind
the pole 29# of line 117, forming the short circuit of the phases A and B of
different lines and generating the peak current over 1000A
• After tens of milliseconds, the phase C conductor at the pole 52# of Line 115
also falls off the cross arm, causing short circuit of Phase A and C. When the
peak of short-circuit current exceeds 5000A, the relay protection at the outlet
of the line is operated. After the switch trips, the system runs normally,
indicating that the insulation of the original breakdown point of the pole 29# of the line 117 is restored.

Typical Use of PMU: Disconnection grounding fault location

• 2018-10-05，15:27:45:395312， First alarm, the assignment notice is received.
“Allocation notice: 10kV Section 2 Phase A is connected to the ground at 15:29”  “Allocation notice: 10kV Section 2 Phase A
grounding disappear at 15:47 ”
• Patrol to confirm the break of 127-1-28# of Line 121
branch
• Timely discovery of broken wire contact, to
avoid passers-by close to the electric shock. It
is speculated that the ground jitter of the
broken insulated conductor causes multiple grounding. After the metal core is retracted
into the insulation layer, the phase loss
operation will result in the bus voltage
returning to normal
• During this time, typhoon "Connie" passed
through, so it is speculated that the
disconnected line was caused by typhoon.

Typical Use of PMU: Big Data + AI Identification Guide to Find Fault Switches

It is Small resistance grounding system, PMU sensor configuration.

whole process of fault identification and confirmation:
• 2020.11.25 - 2021.2.5, C28YC line had 5 grounding
alarms, and all the alarm had the same
characteristics, but the fault point could not be found
during on-site inspection.
• The AI identified a match between the characteristics
of the second half of the cycle and a type of waveform
in the historical database, and deduced that it was a
switch defect.
• On February 5, 2021, the on-site personnel had a target
in mind and found the switch fault at pole 84.

Typical Use of PMU: Line Insulation Warning - Reason: Meteorological Disaster

Line Neutral Grounding Mode: bus 1 arc suppression coil,
bus 2 ungrounded
PMU Sensor Layout Details:

System warning times: 13 times
Fault evolution process: on the afternoon of August 13, 2019, there were 13 disturbances, all indicating that they occurred in the
same line section. The zero-sequence voltage rises continuously from 20V at the beginning of the warning to 30V at the end. The
zero-sequence current increases from 3A to 5A, and the insulation of the line deteriorates. Due to the backlog of emergency repair
tasks caused by typhoon one day ago, the priority of early warning and shortage elimination work has been postponed. After 9
hours deterioration into a short circuit, protective action trip, resulting in power failure.

Typical Use of PMU: Line Insulation Warning - Cause: Conflict with Trees

Starting from 21 o 'clock on 2020.5.25, nearly one hundred weak disturbance events
were perceived, all of which occurred in the same place.
The damping resistance of the arc suppression coil in the station is seriously heated.
The maintenance personnel patrolled the line according to the warning information.
After clearing the tree barriers and removing the defects, the insulation of about 14
points of the line was completely restored and the system returned to normal.

Typical Use of PMU: Line Fault Warning - Cause: Bird Damage
Line Neutral

System warning times: 10
Fault evolution process: From 19:57:41 to 22:48:18 on July 7, 2018, dozens of alarms were raised in the same place.
The time between two faults is getting shorter and the frequency is getting higher, which shows the trend of developing
into permanent single-phase grounding faults. At around 10:50, the
maintenance personnel manually pulled the switch
on the site, destroyed the bird's nest in the fault section, closed the switch to restore power transmission, the fault disappeared.

Typical Use of UCMU : Equipment Failure Warning - Cause: External Force
Damage the Cable

Line neutral grounding mode: neutral
grounding through arc suppression coil
SMS warning times: 1

Fault Evolution Process: Multiple instantaneous
grounding occurred since 15:22 on April 24, 2020, and the
system pushed multiple warning information. In order to avoid frequent warning of short messages caused by
instantaneous disturbance, the system sets three
instantaneous grounding times within 20 minutes as the
condition for pushing warning short messages. This
condition can be improved through the accumulation and
learning of big data by setting frequency. By 17:46, it
became permanently grounded and lasted for 55 minutes.

Typical Use of PMU: Equipment Failure Warning - Cause: Switchgear Insulation
Deterioration

System Warning Times: 4
Fault Evolution Process: During the period
of 2020.11.21 to 2020.11.24, there was 4
instantaneous grounding and 1 permanent
grounding, and it eventually evolved into a
short circuit fault. The system recorded 5
grounding faults with the same fault interval,
imilar waveform and obvious arc pull
characteristics, which were judged to be insulation faults at the same location.