The synonyms are words that, employed in the same context, have their meanings very similar and, therefore, they collaborate so that the repetition does not happen in excess and impoverishes its text.
In addition, the use of synonymous expressions makes explicit to the reader his broad vocabulary knowledge on the subject. That is, varying the way of referring to the same element demonstrates that you have a wider repertoire of reading and reflection on the subject.
Here is an example of how repetition can be resolved in the text:
Civil Defense sees no risk of collapse of the National Museum building, but recommends interdiction of the centennial building. Cracks in the structure of the centenary building provoked after fire demonstrate that coating may fall.
Civil Defense sees no risk of collapse of the National Museum building, but recommends banning the centennial building. Cracks in the structure of the centenary palace provoked after fire demonstrate that coating may fall.
Another way to avoid repetition is to use nominal expressions, not necessarily synonyms, as in the following example:
Exactly six decades ago, on June 29, 1958, a summer Sunday in Stockholm, Pelé started an eternalized goal in the history of World Cups: he killed the ball in the chest within the area of Sweden. She dribbled once on the ground before the headline superstar Gustavsson and finish in the corner of goalkeeper Svensson. By that time, 10 minutes into the second half, Brazil opened 3-1 in the final of the World Cup, against the hosts. The match would still have three more goals (it ended 5-2), but the time when the shirt’s kick 10 entered already proved that the Jules Rimet prize, which awarded the best selection of the planet, deserved another country as owner after Uruguayans, Italians and Germans to erect it.
It is very important that you make reading a daily exercise, just as in writing a text, pay attention to the vocabulary used. Also make sure you consult a traditional dictionary, or a thesaurus, that will only leverage your language repertoire.