Mega MEg31 User manual

MEg 30 - portable version
for LV networks

MEg 31 - portable version
for MV networks

1. Charakteristics
PQ monitor is a multi-function measuring instrument to be used for the measure-
ment and a long-term recording of up to four voltages and four currents, of active
and reactive power and energy in three-phase four-conductor and five-conductor
LV networks, as well as in MV and HV networks. Complying with the EN 50160
standard and with methods of the international standard IEC 61000-4-30, the PQ
monitor analyses all parameters of the voltage quality on voltage inputs U1, U2
and U3.
It registers the events (voltage dips, swells and interruptions) on all the four volt-
ages and it records not only the characteristics of events on voltages as defined by
the standard but also the shapes of all the four voltages and currents at the begin-
ning and at the end of each event – the so-called initial and final details. The initial
detail of an event also comprises the section of time prior to the event while the final
detail also includes the section of time following after this event.
Basing on the measured shapes of currents the PQ monitor enables to assess the
direction of the origination of an event as well as of flicker. By its ability to measure
even small voltages the PQ monitor is also ready for monitoring the voltages be-
tween the neutral conductor and ground. On its fourth current input the PQ moni-
tor enables to carry out the measurement and harmonics analysis of the current of
the neutral conductor. Variably, when using a corresponding sensor the fourth cur-
rent input can also be used for the measurement of other physical quantities, e. g. for
the measurement of temperature.
PQ monitor is provided with a galvanicly separated synchronizing input SYNC.
Its change of state can be registered as an event, too. This makes possible an external
synchronization of the record of shapes of all voltages and of all currents, as well as
a mutual synchronization of a set of several PQ monitors. The PQ monitor has, on its
output, a change-over contact of the polarized relay with a programmable assigna-
tion of the meaning of the signalization.
PQ monitor enables to measure the relationship between the voltage quality and
the power and/or energy. When the preset parameters of voltage quality have been
overpassed, it is possible to switch an external two-state electricity meter or – for op-
erational purposes – to initialize the internal function of the measurement of
“non-quality energy”.
PQ monitor has been designed in the following versions:
MEg 30 – PQ monitor in portable version for LV networks
MEg 31 – PQ monitor in portable version for MV networks
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MEgA Měřicí Energetické Aparáty

MEg 32 – PQ monitor in version for fixed mounting in LV networks
MEg 33 – PQ monitor in version for fixed mounting in MV networks
The following instruments have been designed for PQ monitors in portable version:
–current sensor AMOS PQ (30 A, 100 A, 300 A, 1000 A)
–instrument current transformers MT PQ (1 A, 5 A, 30 A, 150 A).
PQ monitors in version intended for fixed mounting are manufactured with cur-
rent inputs 5 A, 1 A or with a special current input. The versions with current inputs
5 A or 1 A are especially suitable for precise measurements of electric energy. So
that the PQ monitor may be additionally installed for permanent utilization in
substations being already under operation, it is advantageous to use current trans-
formers with split cores MEg MT manufactured complying with Patent Nr. 286255.
Fixed version of PQ monitors with flexible current sensors AMOS can also be deliv-
ered as option.
All versions of PQ monitors for the measurement in LV networks have a
three-phase supply from voltages being measured U1, U2 and U3. In order to pre-
vent the degradation of accuracy and credibility of voltage quality parameters being
measured, a single-phase external supply is used in PQ monitors intended for mea-
surements in MV networks with heterogeneous instrument voltage transformers.
Each version of the PQ monitor is provided with an internal back-up battery
which enables the monitor to be operated during up to 5 minutes without the exter-
nal supply.
The measuring ranges of phase voltages of PQ monitors for LV networks are
from 0 Vef to 480 Vef and of those for MV networks from 0 Vef to 140 Vef.
Phase-to-phase voltages can be registered and analysed by calculation as well.
The basis of all version of PQ monitors is a signal processor with a high-capacity
non-destructive data memory which enables a really long-term (more than 1 year)
antonomous performance. The parallel and continuous performance of all measur-
ing, visualization and communication functions represents a substational character-
istic of the PQ monitor. A high accuracy and independence on operational
conditions is ensured by a high-quality A/D converter with a minimized extent of
analog circuits and with a correction of errors of the whole measuring string made
by calculation.
By means of communication interfaces the PQ monitor can also be used as an in-
telligent peripheral unit of large SCADA systems and energy systems of industrial
enterprises and agglomerations.
Like all other measuring instruments MEg being manufactured till now, the PQ
monitor enables not only the teleparametrization of measuring functions but also
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PQ monitor – MEg30, MEg31, MEg32, MEg33

the telereprogramming of their structure according to user’s requirements and/or
the teleprogramming of newly developed functions.
2. Principle of measurement and of data processing, organization
of the data memory
The measurement of four voltages and of four currents is based on sampling them
with frequency 5120 Hz. The total number of 1024 values with resolution of 14 bits
are always sampled in 200 ms long intervals, following one after another without
timeouts. After transformation into the frequency area, 512 complex harmonic com-
ponents with step 5 Hz (i. e. 51harmonic components regarding the multiple 50 Hz)
and 461 interharmonic components are then calculated from these values. The mag-
nitudes of voltages U1 to U4, currents I1 to I4 and “control signals” (ripple control)
are calculated from the absolute values of the complete spectrum. Active and reac-
tive power of individual components as well as the unbalance are calculated from
complex components.
The data from channels U1, U2 and U3 for evaluating the events and flicker on
voltages are processed in the time area. The square of the TRMS value for the
elapsed period (20 ms) is calculated after every 10 ms. Frequency is calculated from
the data of channel U1.
Corrections of DC components, corrections of strengthening the current sensors,
of voltage and current measuring channels and frequency characteristics including
corrections of a possible phase shift between individual measuring channels are
made during the calculations. The tables of calibration constants are a part of the
configuration. None up to 100 various tables of calibration constants can be stored in
the memory of the firmware depending on the set of the whole measuring string
(measuring converter + measuring channels).
The non-destructive data memory, type FLASH with capacity of 2 MB (4 MB as
option) is divided into five circularly organized areas. The first area shall be used for
recording the development in time of RMS values of measured voltages, currents
and power in a complex form. Detailed data on voltage quality in the elapsed week
shall be stored in the second area. The third data area includes unified data with a
list of events according to methodology of ČSN EN 50160 and the fourth data area
includes a detailed record of the development of RMS values of the half-periods of
voltages U1, U2, U3, U4 and currents I1, I2, I3, I4. The fifth data area includes com-
pressed weekly data on quality. The ratios of ranges of individual areas of the data
memories can be mutually changed respecting the user’s requirements.
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MEgA Měřicí Energetické Aparáty

The basic setting of ranges of the circular areas of the 2 MB memory has been chosen
as follows:
–recording of average RMS values of four voltages, four currents and three real
and three imaginary components of the power; the data memory will be suffi-
cient for recording during 30 days when the records are made with step 1 min
–recording of the list of events with capacity of more than 910 events
–recording of a detailed development of events for more than 180 last events
–recording of compressed weekly data for the period longer than 52 weeks.
When extending the data memory to 4 MB it is possible to extend anyone of the
above-mentioned data areas, e. g. the area of recording the average values and the
area of recording the list of events.
3. Description of measuring functions and of input/output
functions of the PQ monitor
3.1 Function of monitoring (time recorder, type MDS)
Average RMS values from all periods within the chosen step are being recorded
when the monitor operates in this function. Average values of up to four voltages,
four currents and three active and reactive powers (U1, I1), (U2, I2), (U3, I3) are
being recorded according to setting. Basing on these recorded data, real power fac-
tors and energies are then calculated in the higher SW. When a suitable sensor is
installed, another physical quality, e. g. the temperature can be recorded instead of
the current I4.
3.2 Function of voltage quality (monitor, type QN)
The following ten-minute data can be recorded here:
–average frequency, maximum and minimum 10 s frequency derived from U1,
–numbers of overpassing the 10 s values of frequency of four limits defined by
ČSN EN 50160,
–values of voltage unbalance calculated from the negative-sequence and the pos-
itive-sequence voltage component as well as from phase-to-phase voltages,
–average and maximum RMS values of voltages U1 to U4 and currents I1 to I4,
minimum values of voltages U1 to U4 from the 0.2 s long intervals,
–average values of five selected harmonic components of voltages U1 to U4 and
currents I1 to I4 in the range of the 2nd to 51st harmonic,
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PQ monitor – MEg30, MEg31, MEg32, MEg33

–average values of the basic harmonic of voltages U1 to U4 and current I1 to I4,
–values Umax95 and Umin95 of voltages U1 to U3,
–values Umax and Umin (0.2 s) of voltages U1 to U3,
–values of flicker Pst of voltages U1 to U3,
–magnitude of THD of voltages U1 to U3 in relation to the harmonics and to all
interharmonic components,
–magnitudes of ripple control signals on voltages U1 to U3,
–total duration of dips, swells and interruptions of voltages U1 to U3.
The function of voltage quality can also be used in case of a single-phase or
two-phase measurement. The recorded data enable to obtain a detailed survey of
voltage quality parameters for the elapsed week and to evaluate the quality under
changed requirements of the standards.
3.3 Function of recording the events (statistic voltmeter of events)
The function of recording the events operates over the quantities U1 to U3 and I1 to
I3. Every new event is recorded into the list of events and into a detailed record.
Beside the parameters of events unified by standard ČSN EN 50160, i. e. the time
of originating and ending of an event with resolution to 10 ms, the list of events in-
cludes the values of maximum deviations of voltages U1 to U3 from the nominal
value.
Adetailed record of events includes the developments of RMS values calculated
for voltages U1 to U3 and currents I1 to I3 after every 10 ms for the elapsed 20 ms.
The total duration of the record of the initial detail of an event makes 0.6 s from
which the interval of 0.2 s is being recorded prior to the origination of an event. The
total duration of the record of the final detail of an event makes 0.6 s from which an
interval of 0.2 s is being recorded after the ending of an event. The length of these
intervals can be changed programmably.
3.4 Function of compressing the weekly voltage quality data
This function serves for a long-term archiving of weekly quality parameters of volt-
ages U1to U3 complying with ČSN EN 50160. The following data can be recorded:
–number of 10 s intervals when the frequency overpassed the preset limits 47 Hz,
49.5 Hz, 50.5 Hz and 52 Hz,
–number of 10 s intervals in which the mean value of the voltage lied outside the
tolerances 90% Unom to 106% Unom and 110% Unom,
–order of two-hour intervals in which the Plt value was ³1.0,
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MEgA Měřicí Energetické Aparáty

–number of ten-minute intervals in which average value of the 2nd to 25th har-
monic was higher than the value defined by the standard,
–number of ten-minute intervals in which the THD for the 2nd to 40th harmonic
was higher than the value defined by the standard,
–number of ten-minute intervals in which the average value of unbalance was
higher than the limit defined by the standard,
–the number of 3 s mean values of voltage components with frequency of the rip-
ple control signal, which overpassed the limit defined by the standard, is being
recorded for each day of a compressed week.
3.5 Function of oscilloscopic measurements
The function of oscilloscopic measurements serves for checking the correct connec-
tion of the set the PQ monitor, the correct choice of measuring ranges and the correct
orientation of current sensors. A notebook with a series interface USBII is used for
displaying the shapes of voltages U1 to U4 and currents I1 to I4. The recording with
duration of 2 periods (40 ms) can be started case by case or repeatedly.
3.6 Communication function
The basic communication interface of the PQ monitor is a series interface USBII with
the data transmission rate up to 460.8 kbit/s. This enables to read out the content of
the 2 MB data memory during about 2 minutes. It is also possible to choose another
transmission rate (921.6 kbit/s).
Alternatively, the PQ monitors for fixed mounting can be ordered with interface
RS 232 or with another series interface according to the customer’s requirement
(RS485, …).
3.7 External input
The external input is a two-value one and it enables to connect DC and AC voltages
in the range of 24 V to 230 V. The decision making level is at 15 V. The external input
can generate an event without recording the detail of the event. The front edge or
the trailing edge of the voltage of the external input may be active depending on
programming.
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PQ monitor – MEg30, MEg31, MEg32, MEg33

3.8 Relay output
The relay output is made by a change-over contact of the polarized relay and one or
more of the following meanings can be assigned to it by the program:
–voltage U1 to U4 outside the chosen tolerances,
–frequency outside the chosen tolerances,
–flicker Pst higher than 1.0,
–any harmonic component overpassed the chosen limit,
–THD overpassed the chosen limit,
–unbalance overpassed the chosen limit,
–the average RMS value of the current for 10 periods overpassed the chosen limit,
–conversion to supply from internal battery,
–change of state of the contact in case of the change of the voltage on the external
input enables a mutual synchronization of more PQ monitors installed in one
substation.
3.9 Signalization by LEDs
The indication of state of the PQ monitor is signalized by the diode OPERATION
(PROVOZ) which is lighting permanently at the external supply (supply from mea-
suring inputs or external supply) and intermittently with frequency 5 Hz at the sup-
ply from the internal battery. The lighting of this diode can be assigned to the
indication of state of the relay output by program.
In a preset tolerance band (90% Unom to 106% Unom) the LED diodes U1, U2 and
U3 indicate the state of voltages U1, U2, U3 by permanent lighting and by intermit-
tent lighting withf=1Hzthey signalize that the respective voltage is outside the
preset tolerance band.
3.10 State of battery charge
Under reference conditions and at its full charge the internal battery ensures the
supply of the PQ monitor during 5 minutes. Complying with the recommendation
IEC 61000-4-30 and in accordance with the meaning of data measured in the course
of failures in the distribution networks, the supply from the internal battery shall be
automatically switched-off after any interruption of the external supply lasting
more than 1 minute. The discharging of energy of the battery at the interruption of
the external supply with duration of more than 5 minutes is thus prevented and – af-
ter a restored supply and its subsequent interruption due to e. g. switching-in into
short-circuit – the instrument is able to remain in operation for a further 1 minute.
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MEgA Měřicí Energetické Aparáty

In order to save the energy of the internal battery, it is recommended to suppress
the unnecessary (in this case) one-minute back-up supply of the monitor before
each planned disconnection of measuring conductors from the supply voltage. This
shall be done by using the notebook with the started program of the PQ monitor
where the item Uspat shall be updated in menu Measuring instrument.
4. Technical data
4.1 Measurement of voltages
Unom of phase voltages U1, U2, U3, U4: 230 V
Range of measurement of phase voltages: 0 to 2 Unom
Highest permissible phase voltage: 480 Vef
Accuracy of voltage measurement:
± 0.1% of the measured value ± 0.1% Unom at 0.8 Unom to 1.2 Unom
± 0.2% of the measured value ± 0.2% Unom outside 0.8 Unom to 1.2 Unom
Resolution: 0.1% Unom or better
Temperature coefficient: better than 0.2% Unom/10°C
4.2 Measurement of currents
Accuracy of measurement:
± 0.2% of the measured value and 0.2% Inom at 0.1 Inom to 1.2 Inom
± 0.5% of the measured value at 1.2 Inom to 2 Inom
Resolution: 0.1% Inom or better
Temperature coefficient: better than 0.2% Inom/10°C
Highest permissible current loading: 5 × Inom during 1 s
Measuring string AMOS PQ - MEg30
Inom at shape coefficient K = 1.11: 30 A, 100 A, 300 A, 1000 A
Range of measurement: 0 to 1.2 Inom
Accuracy of measurement: 0.1% Inom
Linearity of measurement: better than 0.5% Inom
Change of the measured value with the
change of position: 1% Inom
Measuring string MT PQ - MEg30
Inom at shape coefficient K = 1.11: 1 A, 5 A, 30 A, 150 A
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PQ monitor – MEg30, MEg31, MEg32, MEg33