Quality of service

The quality of service provided by REN, understood in terms of security
and continuous supply of electrical energy with the necessary technical
characteristics, once again reached a high level, maintaining and consolidating a
trend observed in previous years towards a gradual and sustained improvement
in the performance of the National Transmission Grid (RNT).

The figures recorded by three (ENS, EIT and SARI) of the five general indicators
for service continuity established in the Quality of Service Regulations, were the
second best ever, thereby placing REN on a level with the world’s best companies
in a similar field. The remaining two indicators (SAI FI and SAIDI ) recorded the
third best figures ever. The Equivalent Interruption Time (EIT), an indicator of
overall performance commonly used by electrical utility firms, was 5.4 seconds,
the second best figure ever, equivalent to energy not supplied of 8.6MWh. That
is to say, REN fed electrical energy to the various consumer delivery points
99.99998% of the time (almost 999 hours, 59 minutes and 59 seconds, for every
1 000 hours).

In 2013, the monitoring of voltage waveform quality continued at delivery points
and interconnecting points on the RNT.

The measurements carried out continued to show results that, with a reduced
number of exceptions in individual and localised cases, reflect the figures
recommended in the Quality of Service Regulations.

The overall level of electrical energy quality depends on the number of incidents
recorded or with impact on the transmission grid. In 2013, the number of
incidents and disturbances was 249 (35% more than in 2012), 208 of which
originated in the Very High Voltage Network (VHV ), 20 in the High Voltage
Network (HV ) and 21 in other grids but with an impact on the REN networks VHV
and HV . This increase was reflected above all in the incidents that occurred on
19th January, numbering 33 in total, due to the storms and strong winds affecting
the Greater Lisbon area.

Only eight incidents (3.2% of the total) actually caused interruptions to the
supply of electricity to clients, having caused eight interruptions of consumption
at delivery points.

Another way of highlighting the performance of the transmission grid is through
an indicator referred to as “Vulnerability”, which expresses the capability of the
transmission grid to not discontinue the supply of electrical power to consumers
following an incident, regardless of its origin (including incidents caused by force
majeure). This indicator is a ratio of the number of supply interruptions to the
number of incidents.

In 2013, the transmission network registered on average 0.0120 long interruptions
(> 3 min) and 0.0201 short interruptions (between 1 sec and 3 min) per incident.

Network behaviour

During 2013, the major congestions that occurred in the RNT were associated
with outages of grid elements, which were solved through the generation of
network constraints and through the introduction of topological changes to the
network. In this field, it is particularly worth noting the outages that occurred
on the corridor between Recarei and Riba d’Ave that, aside from topological
measures, also required the mobilisation of generation at the Tapada do Outeiro
plant and reduction of hydropowered generation located in the Cávado basin.

In 2013, the national consumption of electricity remained at identical levels to
those seen in 2012, leading to a continued excess of energy in the RNT, and
consequent difficulty in controlling voltage. The aforementioned difficulty
was overcome by implementing measures such as turning the Sines plant into
the technical verification headquarters for the day market, limiting output on
subsequent intraday markets, the disconnecting of MHV lines or requesting that
the operator of the National Distribution Grid disconnect their capacitor banks.

Finally, also of note in 2013 was the fact that new maximums for wind energy
production were once again recorded, both with regard to energy and peak
production. Once again the national electricity system managed to store all this
production without having to introduce reductions.

Availability

The Combined Availability Rate, a regulatory indicator introduced by ERSE
in 2009, reached a new historic record in 2013, with a value of 98.89%. The
figure below shows the annual evolution of this indicator in the last five years.

Its progressive improvement highlights the obvious evolution in terms of
coordination and planning of grid outages during the period in question.

Performance of transmission network assets

In 2013, RNT lines had a satisfactory overall performance, in spite of the adverse
weather conditions seen on 19th January. On this day, 41 faults were registered
on lines, including the collapse of four pylons in the Lisbon region. The number
of faults per 100km of circuit thereby saw an increase of 33% compared to the
previous year. Without the faults that occurred on that day, the figure would be
close to that seen in 2012 (+4.8%). The graph below illustrates the performance
of lines in the last 5 years, with regard to the number of faults per 100 km
of circuit.

The overall availability rate for line circuits, including terminal panels, was 99.02%,
a significantly higher figure than the one recorded in the previous year (+0.45%).

In general, all substations recorded favourable behaviour in their service
performance. In spite of this, there was a slight increase in the number of
damaged transformers and circuit breakers compared with the 2012 figures,
although, in the majority of cases, there were no consequences to network
operation. The overall availability rate of transformers and autotransformers
(including the respective panels) stood at 98.48%, a similar figure to that seen in
2011 (+0.03%). This indicator is mainly affected by remodelling and replacement
work on HV equipment and transformers during 2013.

More in-depth technical detail is available in the Quality of Service report
published annually by REN.