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TECHNICAL REQUIREMENTS
FOR THE CONNECTION OF GENERATION FACILITIES
TO THE HYDRO-QUÉBEC TRANSMISSION SYSTEM
SUPPLEMENTARY REQUIREMENTS
FOR WIND GENERATION
MAY 2003
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Langue applicable:
La version anglaise est pour le bénéfice de l’utilisateur seulement. Dans l’éventualité où
une divergence intervient entre la version française et la version anglaise, la version
française est la version originale et doit s’appliquer lorsqu’une question concernant
l’interprétation de son contenu est soulevée.
Governing lanquage :
The English version is for the user’s convenience only. In the event of any discrepancies
between the French version and the English version, the French version shall be the
original and shall be the governing language in the event of any question concerning the
meaning of its terms.
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1. Background
The document “Exigences techniques relatives à l’intégration des centrales au réseau de
transport d’Hydro-Québec ” issued in May 1999 by Hydro-Québec TransÉnergie states
the requirements which must be met by generators wishing to connect a generating
station to Hydro-Québec’s transmission system.
Since the document was published in May 1999, wind power generation technology has
been evolving rapidly.
To cover the additional technical aspects associated with this type of generation
technology, specific requirements are required. They complement or modify those stated
in the May 1999 document. The requirements mentioned in this document take
precedence over those in the May 1999 document.
The additional requirements associated with wind power generation are presented in the
pages that follow.
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2. Definition
The May 1999 document dealt with connection substations. To be in line with the
document “Hydro-Québec Open Access Transmission Tariff,” the expression
“connection substation” has been replaced with “switchyard.”
Based on the description provided in the “Hydro-Québec Open Access Transmission
Tariff” (Attachment J, Section B, Subsection 1), “switchyard” is defined as follows:
Substation through which the generator’s facilities are connected to the
transmission system. It is generally a transforming substation located near a
power plant. The switchyard consists of the high-voltage portion of the substation
and includes one or more step-up transformers from the step-up transformer lowvoltage terminal. When more than one output level is required from switchyard
transformers, those other levels are also included.
Diagram 1 illustrates this concept for a wind farm.
Diagram 1: Switchyard boundaries for a wind farm
Transformer lowvoltage terminal
Switchyard
HIGH-VOLTAGE SWITCHING
High-voltage connection
point
FOR REFERENCE PURPOSES ONLY
(Does not display all of the required equipment or apparatus)
As shown, a wind farm switchyard includes the following: first output level from the
low-voltage terminal near the wind turbine, connection to the second output level, step-up
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transformer(s) at the second output level, and the high-voltage portion up to the
connection point to Hydro-Québec’s transmission system.
3. General requirements regarding the design, construction and operation of the
generator’s facilities
The generating facilities connected to Hydro-Québec’s transmission system should
remain in service as long as possible without tripping during severe events that cause
voltage or frequency variations. The reason is, on the one hand, to not interfere with the
automatic controls in use on the system, and on the other, to help restore voltage and
frequency.
To this end, a generator’s facilities must be designed, built and operated so as to remain
in service and not cause any unit to trip during the voltage and frequency variations
shown in Tables 1 and 2 in Section 8.1. The requirement for frequency presented in
Table 2 is also applicable to generating stations connected through the distribution
system.
4. Voltage regulation
Voltage regulation is required to ensure transmission system stability and reliability. For
voltage regulation to be efficient, most of the generating stations must take part in the
process.
For wind farms capable of voltage regulation, the transmission provider may require,
based on the conditions described below, that the generator’s facilities take part in
regulating the system voltage continuously, dynamically and rapidly. Continuous,
dynamic and fast control must be comparable to that provided by a static compensator.
All of the alternators capable of regulating voltage (such as wind turbines equipped with
double-fed asynchronous generators or those equipped with a converter) must be
designed to continuously regulate voltage on Hydro-Québec’s transmission system in
transient, dynamic or steady state. To this end, the alternators must be equipped with an
automatic voltage regulation system and be capable of supplying or absorbing, in steady
state, the reactive power corresponding to the power factor specified in Sections 5 and 6
of this document.
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5. Design power factor for synchronous generators
Sufficient supplies of reactive power are required on the transmission system in transient,
dynamic or steady state to ensure transmission system stability and reliability.
For wind farms equipped with synchronous generators connected to the transmission
system through a converter, the generator’s facilities must be designed to supply or
absorb, at the converter outlet (system side), the reactive power that corresponds to an
overexcited or underexcited rated power factor equal to or less than 0.95. The reactive
power must be available over the entire real power generation range.
6. Design power factor for asynchronous generators
For wind farms equipped with asynchronous generators not capable of dynamic voltage
control, a unity power factor must be provided at the connection point.
The number and power rating of the capacitor banks used to correct the power factor
must be established by the generator to avoid self-excitation problems given the different
modes under which the facilities are operated. When the generating station is connected
directly to the transmission system, to avoid the occurrence of self-excitation phenomena,
generators may not be able to install a sufficient number of capacitors in their facilities to
comply with the unity power factor at the connection point. Generators would then have
to compensate for this reactive power deficit by paying for the addition of reactive
compensation equipment at more appropriate points on Hydro-Québec’s transmission
system.
For wind farms equipped with asynchronous generators capable of voltage regulation
(such as wind turbines equipped with double-fed asynchronous generators or those
equipped with a converter), the generator’s facilities must be designed to supply or
absorb, at the generating unit outlet (system side), the reactive power that corresponds to
an overexcited or underexcited rated power factor equal to or less than 0.95. The reactive
power must be available over the entire real power generation range.
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7. Requirements regarding auxiliary services
Auxiliary services required to operate the wind farm must remain operational and not
cause, either directly or indirectly, any unit to trip during the voltage and frequency
variations described in Section 8 below.
This requirement is also applicable to the auxiliary services of any wind farm connected
to Hydro-Québec’s transmission system through the distribution system.
8. Requirements regarding protection systems
8.1 General requirements
Generating facilities connected to Hydro-Québec’s transmission system must remain in
service without tripping for as long as possible during severe events resulting in transient
disturbances that affect voltage, power or frequency on the transmission system.
Protection systems, used to protect the generator’s facilities, must be sufficiently
selective to prevent undesirable tripping during such events. Thus, during power swings,
no protection system should cause, either directly or indirectly, any unit to trip for the
following voltage and frequency variations:
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Positive sequence voltage variations at fundamental frequency as shown in Table 1:
Table 1
Minimum time periods during which wind farms must remain in
service without tripping during voltage variations
Voltage (p.u.) note
Duration
V < 0.60
0.10 second
0.60 ≤ V < 0.75
0.25 second
0.75 ≤ V < 0.85
2.0 seconds
0.85 ≤ V < 0.90
300 seconds
0.90 ≤ V ≤ 1.10
permanent
1.10 < V ≤ 1.15
300 seconds
1.15 < V ≤ 1.20
30 seconds
1.20 < V ≤ 1.25
2 seconds
1.25 < V ≤ 1.40*
0.10 second
V > 1.40 p.u.*
0.03 second
Note: Positive sequence voltage at fundamental frequency
*
: Facilities that use power electronics must remain operational throughout the entire
voltage range except for voltage levels greater than 1.25 p.u. where temporary
blocking is allowed.
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Frequency variations as shown in Table 2. However, a more stringent no-tripping
requirement could be imposed to meet specific needs identified during the integration
study.
Table 2
Minimum period of time during which wind farms must remain in
service without tripping during frequency variations
Frequency (Hz)
Duration
F < 55.5
Instantaneous
55.5 ≤ F < 56.5
0.35 second
56.5 ≤ F < 57.0
2 seconds
57.0 ≤ F < 57.5
10 seconds
57.5 ≤ F < 58.5
1.5 minutes
58.5 ≤ F < 59.4
11 minutes
59.4 ≤ F ≤ 60.6
Permanent
60.6 < F ≤ 61.5
11 minutes
61.5 < F < 61.7
1.5 minutes
F ≥ 61.7
Instantaneous
The requirement regarding the ability of protection systems to withstand the frequency
variations listed in Table 2 is also applicable to any wind farm connected to HydroQuébec’s transmission system through the distribution system.
8.2 Voltage protection
Voltage protection includes an undervoltage function as well as an overvoltage function.
The protection must be sufficiently selective to prevent undesirable tripping during
events on the main grid resulting in transient disturbances. Voltage protection must
therefore comply with the no-tripping requirements listed in Table 1 of Section 8.1. The
durations shown in the table set the minimum time-lags which the protection system must
have in the corresponding voltage zone. For instance, referring to Table 1, voltage
protection with a threshold set to operate in the (0.85 ≤ V < 0.90) voltage zone should
have a minimum time-lag of 300 seconds. The voltage protection must be coordinated
with the other protection systems in use and initiate the tripping of the generating station
to prevent it from being operated under unacceptable voltage conditions.
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8.3 Frequency protection
Frequency protection includes an underfrequency function as well as an overfrequency
function. Frequency protection must be coordinated with the other protection systems in
use and initiate the tripping of the generating station to prevent it from being operated
under unacceptable frequency conditions. It must be set at threshold and time-lag values
that are sufficiently selective to prevent operation during transient events occurring on the
main grid. At no time should the protection system settings interfere with the means
implemented by the transmission provider to restore the system frequency, which may
vary after a disturbance.
Frequency protection systems must comply with the no-tripping requirements listed in
Table 2 of Section 8.1. The durations shown in the table set the minimum time-lags
which the protection system must have in the corresponding frequency zone. For
instance, referring to Table 2, frequency protection with a threshold set to operate in the
(58.5 ≤ F < 59.4) frequency zone should have a minimum time-lag of 11 minutes.
9. Fast voltage variations and flicker
Fast voltage variations and flicker are disturbances which can occur randomly or
periodically and in so doing disrupt sensitive loads.
Paragraph 1 of Section 4.3.1 of the May 1999 document lists a few examples of potential
causes of such disturbances. To this list should also be added the continuous power
variations caused by wind turbines.
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10. Technical information to be transmitted by the generator to the transmission
provider prior to the integration study
In addition to the information contained in Appendix B of the May 1999 document, the
following information must also be provided:
For wind turbines equipped with double-fed asynchronous generators, direct-drive wind
turbines with permanent magnet generators, wind turbines equipped with converters, and
all other wind turbines using the latest technology:
- Detailed models and associated machine parameters, using standard IEEE models
as a reference;
Or detailed models and associated machine parameters that can be used by the
transmission provider for dynamic simulation studies using Power System
Simulator (PSS/E) software;
- Detailed models and associated converter parameters that can be used by the
transmission provider for dynamic simulation studies using Power System
Simulator (PSS/E) software.
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