can also further obtain the characteristics of users’ electricity
consumption behavior and types of users, and provide users
with user portraits and better electricity experience.
Most Existing NILM methods can be divided into event
based NILM methods that focus on temporal data and non-
event based NILM methods that focus on steady data [7].
The event based NILM methods generally including event
detection and classification steps [8], hence, the accuracy of
event detection influences the performance of NILM methods
directly. Three of the typically event detection methods are
CSD (cumulative sum detector) [9], GLRD ( generalized like-
lihood ratio detector) [10] and GFD (goodness-of-fit detector)
[11], all of which require fixed window size for reference
set and current set [8]. The non-event based NILM methods
usually take every sample of aggregated power data into
account [8], hence, the input data may be too large to analysis
and leading to computationally expensive and time consuming.
Although more progress has been made in the research of
non-intrusive load monitoring algorithms, good identification
results have been achieved on some datasets. However, there
are few studies on data collection of non-intrusive load data,
and the current application of non-intrusive load monitoring
still has several shortcomings in data collection:
1) Large Data volume. Non-intrusive load data is often
months or even years of data. If we want to obtain better
load identification effect, we need high frequency load
data. The continuously collected data makes the data
volume of non-intrusive load very large, which makes
the storage and computing resources required for non-
intrusive load identification very high, which hinders the
application of non-intrusive load identification.
2) Varies data length. The existing non-intrusive load data
collection method is a simple fixed frequency, random
start/stop way to collect data. The collected data is a
single time series of varying lengths. Moreover, due to
the random and unfixed time when users use electrical
appliances, and a large amount of time (such as night)
when electrical appliances are not used, load fluctuations
are randomly, discrete and non-uniform scattered in the
time series. This results in the variable length of the
collected non-intrusive load sample data, which affects
the performance of the non-intrusive load identification
algorithm.
Hence, in this paper, a non-intrusive load data collec-
tion strategy based on event trigger and sliding-time-window
is proposed, by combining event-trigger and sliding-time-
window, the data volume of non-intrusive load collected can be
significantly reduced while the size of data samples collected
each time is fixed. The contribution of this paper can be
summarized as follows:
1) Through the event-triggered collection strategy, only the
data segment with load hopping is collected, which
greatly reduces the amount of non-intrusive load data
collected.
2) The data collecting method of sliding window ensures
that the collected data is a data segment of fixed length,
and contains the complete data at the moment of load
change, which is more convenient for data processing.
3) The comparative experiment proves the effectiveness
of the method. On the REDD dataset [12], seven
non-intrusive load monitoring algorithms included in
NILMTK [13], [14] are used to compare the perfor-
mance of the data before and after using the acquisition
strategy. The experimental results show that the pro-
posed data collection strategy not only greatly reduces
the data size, but also improves the performance of the
non-intrusive load identification algorithm.
In the following content of this paper, section II gives a
detailed analysis of the problems solved in this paper,and
introduces the framework of non-intrusive load data collection
strategy based on event-trigger and sliding-time-window with
its detailed data collecting process. section III introduces the
performance evaluation of the proposed algorithm on REDD
datasets, and finally concludes the paper in section IV.
II. PROPOSED DATA COLLECTION STRATEGY
A. Problem Introduction
The existing non-intrusive load data collection is mostly s-
ingle time series data, which can be divided into total load data
(meter data) and load data of single appliance. The acquisition
frequency varies from 1min to 250kHz, the collected data
include V(Voltage), I(Current), P(active-power), Q(Reactive
Power), S(passive-power), F (Frequency), PF (Power Factor),
One or more of E(Energy). The collection time varies from
several months to several years for low-frequency data, while
for high-frequency data, due to the large amount of data, the
published data is often only months or even weeks.
Research shows that high frequency data has great advan-
tages over low frequency data. For example, two devices of the
same type can even be distinguished using raw data sampled
at 1MHz. However, the acquisition of high frequency data is
accompanied by a thousand fold increase in the size of the
dataset. For example, the original high frequency data of uk-
dale (16kHz) generates 8.3GB of data per day, which results
in some high frequency data sets with only a few minutes
of data to control the size. This causes a lot of trouble for
researchers to study high-frequency NILM data. In terms of
the format of data sets, low-frequency data can often provide
original data, while high-frequency data usually only provide
compressed data (FLAC or WAV format) because the original
data is too large.
The collection frequency, duration and volume of data sets
commonly used in NILM are shown in the following Tab.I:
Therefore, if it can effectively reduce the size of NILM
dataset, it means that the terminal NILM data collection
terminal can collect and store data for longer time and more
appliances, while the cloud NILM data storage and analysis
will become easier and cheaper. At the same time, if the
NILM data can be effectively divided into fixed size samples,
the input requirements of different algorithms can be better
adapted, and more algorithms can be better used for analysis.
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